- +10% Morale of armies
- +30% Improve relations
- +10% Imperial authority growth modifier
- −15% Diplomatic annexation cost
- −10% Fort maintenance
- +15% National garrison growth
- +0.05 Yearly inflation reduction
- −0.5 Interest per annum
- +2 Diplomatic reputation
- +2% Missionary strength
- +1 Diplomatic relation
- +30% Reinforce speed
- +3% Discipline
- +50% Chance of new heir
Newborn Ladislaus would have a hard time claiming his legacy, and lost the throne of Hungary after a short civil war to the Polish King Wladyslaw. The Kingdom of Bohemia on the other hand is still divided on the issue. Decades of religious civil wars have left the country ravaged with some parts still dominated by powerful Hussite nobles, heretics to the Catholic faith. Only in Austria, the homeland of the Habsburg dynasty, has Ladislaus been accepted, though his uncle Frederick now rules as his regent.
With the catastrophe of Varna the Hungarian throne is again vacant, and Habsburg supporters remain hopeful that it can be reclaimed for Ladislaus. The powerful groups that deposed the boy king once do not seem disposed to accept him a second time. They may well let their dynamic Hungarian regent Janos Hunyadi lead them instead.The dream of a Habsburg Emperor was not lost with Albert. Upon his death, Frederick, the Austrian regent, was elected to lead the Holy Roman Empire. As the first of his family to sit on the Imperial throne Frederick will leave a legacy for future Habsburgs. Should they choose to pursue his careful policies of diplomatic marriages and patient inheritance planning, the Habsburgs may well build up a position of power unlike that of any family among the kings of Europe. The responsibilities of Imperial rule are great obstacles in themselves. An Emperor must keep the peace in the empire, fight heresy such as the recent Hussites and at all costs protect Christianity from the advancing armies of the Ottomans, a power to which the Habsburgs have already lost one King.
"While other nations do battle, you lucky Austria, you wed." - Maria Theresa of Austria, Last of the Habsburgs (1717-1780)
Austria starts the game as the Emperor of the Holy Roman Empire. It is located in Central Europe, bordered by Bohemia and minor German states to the north and west, Hungary and Cilli to the east, and Venice and Trent to the south.
As the Emperor of the traditionally fractious German HRE states, it is up to Austria to unify the Empire as the famous Habsburgs and stake their claim on history as a world power. The Emperor of the Holy Roman Empire may be called into defensive wars against outside aggressors, and is also tasked with maintaining order in the empire and enforcing religious unity.
- 1 Missions
- 2 Austrian Government Power Structures
- 3 Events
- 4 Reformation
- 5 Strategy
- 6 Idea groups
- 7 Achievements
- Main article: Austrian missions
Austrian missions are focused around uniting the Habsburg lands and uniting the Holy Roman Empire.
Austrian Government Power Structures
Please help with verifying or updating this section. It was last verified for version 1.30.
Austria has two unique government reform power structures available, one at standard game start and the other more advanced form available after completing the Hungarian related mission, Multicultural Empire, triggering the event 'Reform the Austrian Imperial Government?' Interestingly, the player may elect to keep the Austrian Archduchy but add a +2 Max Promoted Cultures modifier instead of adopting the Imperial Austrian Monarchy which makes the choice slightly less straight forward.
The Austrian Archduchy is a unique government type available only for Austria at the standard start that gives a significant bonus to retaining subject nations. Having this government ensures:
- −33% Liberty desire from subjects
- +5% Nobility influence
- +5% Marathas influence
- +5% Rajputs influence
Imperial Austrian Monarchy
The Imperial Austrian Monarchy is a unique government type available only for Austria by mission, Multicultural Empire, that gives a major advantage in diplomatic power income. Having this government ensures:
- Main article: Austrian events
Austria's events deal with Austro-Bohemian relations, instability in Austria's holdings in Hungary, famous people of the time period such as Mozart and Metternich, and the Italian Wars.
Reclaim the Archduchy of Austria
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From Wien, the Habsburg once held absolute power of the Holy Roman Empire, and the very core of their power was the Archduchy of Austria. Now, their empire has long since turned to ash and it is left for us to reclaim the Archduchy and the seat of power in the Empire!
The Emperor DLC significantly changes the game for Austria, with the mission system guiding Austria's expansion and dominance of the Empire.
The Key States and Missions
Bohemia One of Austria's early missions grants a Force PU CB upon Bohemia, once Austria has 5 Electors that have +100 opinion of Austria and supports them for the Emperor. This is fairly easy to accomplish within the first few years of the game. This mission does not require allying all 5 needed electors. Take note of rivalries, as allying rivals can add unwanted -25 penalties with other electors. Also take note of which electors could potentially support others, as electors will not support your candidacy if they are backed by another.
Next is the war against Bohemia. Bohemia is a similarly sized nation to Austria, and also has two small vassals in the Silesia area. Additionally, they can have allies, though they often only have one or two minor princes in the Empire willing to back them. However, despite being outnumbered, the war is easily winnable without calling in allies.
Available allies are somewhat slim. Hungary has a truce with Bohemia, and most of the HRE princes have no interest in attacking Bohemia. The main possible ally is Poland if rivalled to Bohemia. Poland can be promised land to join. But this involves either giving away part of your Bohemia PU, or not giving them land, causing diplomatic consequences.
Bohemia in most cases keeps their starting army on both its forts. Starting the war by rushing either of the forts with your army, and stack wiping the divided stack will help greatly against Bohemia. While they rebuild, you will have time to siege down their forts. A general with high maneuverability, and drilling your troops before the war, both allow your stacks to move faster, making it easier to catch their armies. A morale or discipline advisor is also valuable in making it more likely to stack wipe.
Another key aid in the war is checking the available mercenary stacks for hire. They will be led by their own generals, and a high siege pip can siege down Bohemia's forts much faster.
Once Bohemia is defeated, improve relations with them to positive. If your king dies before relations are positives, the PU will be broken.
Hungary starts off in an Interregnum, and will soon get the same heir as Austria has. The resulting events can result in Hungary naturally falling in a PU under Austria, or Austria receiving a PU CB on Hungary. Additionally, Austria has a mission to receive a CB on Hungary if Austria and subjects development exceeds that of Hungary.
In the early game, Hungary is of little help as an ally as they have truces with multiple nearby nations, and are unwilling to help attack others. Additionally, the truce time for breaking an alliance can add years of delay if unlucky. Finally, the diplomatic slot can be better used for other uses So it is best to not ally or royal marry Hungary. Instead, wait until Ladislaus the Posthumous turns 15. Then Hungary will either willingly join. If not invade. With the aid of Bohemia, it should not be difficult, unless Hungary receives a powerful ally.
Milan starts off the game with an old Duke with no heir. A royal marriage with no alliance can often net a PU, or a full Inheritance of Milan's lands. However if unlucky, Milan has not slipped out of your potential grasp. Two more opportunities await.
Firstly, if the Ambrosian Republic event fires in Milan, both France and Austria as Emperor can receive a force PU CB on Milan. This PU may not last long, as it can be removed if Sforza turns Milan back into a monarchy.
Secondly, through Austria's mission tree, they can obtain a force PU CB on Milan. However, this mission is locked behind directly owning most of Croatia, and the annexing of Venice's non-Milanese Cores in Northern Italy. This adds a significant delay to obtaining Milan.
One key aspect to note. Milan does not start off as an Elector to the HRE. But if an elector is eliminated, and Northern Italy is reined in, Milan can be made an elector. Since you as Austria have a guaranteed means of PU Milan, this can further tip solid control of the Empire to the Habsburgs.
Naples/Two Sicllies starts off the game under an Aragon PU. However, the death of their old starting king will often lead to Naples going free. Austria through its mission tree also receives a Force PU CB on Naples, after obtaining Milan. However, this PU CB is only available if Naples is independent. If not the mission will only grant less valuable permanent claims. So while waiting for the mission to become available, it is worth keeping an eye on Naples and endeavor to keep them independent. If Naples, however, forms the kingdom of the two Sicllies, you will get a PU CB on it instead. I advice you help this to happen, as it is much better than Naples.
Bavaria does not start the game as a starting tag. Instead, the region is divided between multiple tags, which have their own missions to form the tag. While it is common to practice to intervene or use the powers of the Emperor to demand unlawful territory, the Bavarians should be ignored.
The reason for this comes from one of Austria's missions. One of Austria's initial missions is to annex or vassalize 2 of a potential 4 neighboring OPM. Completing this should be held off on until Bavaria is formed. Doing so will shift the mission reward from permanent claims on the Bavarian region to a PU CB on Bavaria.
Like with Milan, giving Bavaria an elector status before forcing a PU on them will help in locking down the elector of the Empire. Additionally, Bavaria is a smaller country than Bohemia, so it is easier to inherit Bavaria, and thus their elector status, than with Bohemia.
Burgundy should be allied and royal married by Austria. The new Imperial incident chain can allow for Burgundy in it entirety to fall under either Austria, France or an ally as a PU. This can fire at any time after their starting king dies. At the start, Burgundy has an only one available free diplomatic slot. So allying them can prevent them allying with any other nation. Thus when the Inheritance fires, they will most likely fall to Austria.
After the event fires, an Imperial incident will fire. France can demand Burgundy for itself, leading to a war between Austria and Burgundy, against France and its vassal swarm. This is likely more difficult than Austria initial early wars, but you will have a year to prepare for the war, and the war will be a defensive one for Austria, meaning your allies can be called in to fend off France.
Poland/Commonwealth is another nation that Austria can receive a PU on through its mission chain. With Silesia under Austria or its vassals, Austria will receive permanent claims on part of Poland's starting lands, that correlate to the lands Austria took in the partitions of Poland(Galicia). Once annexed, Austria will then receive a Force PU CB.
To obtain the best value from the mission, it is advisable to wait for Poland to reach Administrative Tech 10, which will inherit Lithuania forming the Commonwealth. This will create a much larger PU subject for Austria to control. Note however that Krakow should not be taken from Poland before it can form the PLC, as this province is required for the decision to form Commonwealth
Spain/Castile is another option. You do not get a CB through the mission tree. If you have a royal marriage with them, they are not rivaled to you, they do not have an heir, but can have one, they are not under a PU, their ruler age is at least 20,both of you have been rivaled by France and Spain/Castile is not having France's or Austria's dynasty and both of you are at peace, then you will receive an event called "Spain, an Habsburg throne"(for more details, check the The Habsburgs section of the Spanish events part of the Wiki).this will give them a Von Habsburg heir with a very strong claim (100). when he ascends, make sure you have more prestige then them, he has no heir or a heir with weak claim and you have a royal marriage with them and then claim their throne. by then you will probably have Hungary and Bohemia as PU subjects, possibly more PUs (Bavaria, Milan, Burgundy etc ). you will have a strong army by then.so, this will be an easy war. I advice you to PU when the Iberian Wedding has fired or Spain has formed as you will have Aragon too. if event fires early, or you feel you are not strong enough to take down Spain yourself , as Spain can get pretty OP through colonies by mid-1500, then form some powerful alliances before the heir ascends to make it easy, preferably someone who hates them and will always be ready to join you like Britain or Morocco just temporarily and to make the war easier. after the war, you will have a strong empire, with colonies in far-flung regions and Spain's massive colonial navy(and army). after this, either try for PUs on other colonizers or take their colonies for Spain. also, try for a Portuguese PU. you will have all of Iberia, an OP colonizer, a decent navy and also just for the history/roleplay.
Playing Austria is very different from most other nations in the game and therefore offers a unique experience. Austria should retain the title of Holy Roman Emperor in order to maintain their might as a continental power, which means playing the diplomacy and imperial authority game within the HRE. Thankfully, Austria's national ideas form one of the best sets of diplomatic ideas in the game. Maintaining strong allies as well as a fluent diplomacy is also essential as all of Austria's major opponents (particularly France and the Ottomans) have superior military-oriented ideas.
Austria is uniquely situated for forming personal unions. Austrian missions give a casus belli for forming a PU with Bohemia on achieving sufficiently high relations with HRE electors, and another for Hungary after increasing development, regardless of dynasty or royal marriage. In addition, as Emperor, Austria gets more diplomats and more relationship slots, thus allowing more marriages, while high starting (and likely continuing) Prestige makes each marriage more likely to result in dynasties, personal unions, or even outright inheritance. Hungary will very quickly be of the same dynasty by event, regardless of the player's choices, but a marriage makes for easier claiming as well as a great ally.
As a note, economically Austria is relatively weak in trade due to its home trade node being the inland node of Wien. However Austria is unique in that it has one of the few gold mines in Europe (Tirol) and starts out as Emperor with 8 Free Cities () providing a 16 ducat bonus to taxes each year. The inflation from the gold mine can be managed by either Economic Ideas, Austria's third national idea, or by using Papal Influence to choose the Forgive Usury action that reduces inflation.
Austria is also perhaps in the best position to form the Holy Roman Empire, due to starting as Emperor, having several diplomatic oriented national ideas, and their relative position and strength in the empire to enforce their will on the other Princes. Following the steps below will help ensure the player can form the Empire at a relatively quick pace.
- with more princes in the HRE +0.004 per prince over 25
- up to 8 free cities +0.005 per city (with Common Sense)
- peace in the Empire +0.10
- heretic princes −0.01 per prince
- electors that are vassals or missing electors −0.1 per elector (This does not include personal unions, however the −50 penalty in elections for the suzerain still applies)
- Imperial provinces under the control of non-members or subjects of non-members −.005 per province.
Other mechanics can be seen at Holy Roman Empire.
Rein in Northern Italy
The Empire can be greatly strengthened by preventing the Shadow Kingdom event, which causes all of the Italy region to leave the Empire.
Preventing the Shadow Kingdom event requires adding eight more provinces to the HRE: Venice's Treviso, Friuli, and Verona, Urbino's Urbino, and The Papal State's Ancona, Romagna, Umbria, and Roma. If all these provinces are in the HRE from 1490 to 1550, the event cannot fire. The Rein in Northern Italy decision allows some extra flexibility in achieving this goal. This decision adds the emperor's (& subjects') Italian provinces to the HRE immediately, and prevents the Shadow Kingdom event forever. Thus, Austria can take some or all of the provinces with vassals or PUs, without needing to hold them directly to add them to the HRE as normal. This does mean losing the potential Imperial Authority bonus from adding those provinces normally.
One thing to be aware of is the negative effects of war with the The Papal State and control of Rome. Wars obviously involve negative relations with the Papal State, and that reduces Papal Influence. More importantly, a Catholic owning Rome directly or through a vassal causes The Occupation of Rome modifier that decreases valuable diplomatic reputation and gives an extremely large Papal Influence malus, while vassalizing the Papal State causes the Subjugation of the Papacy modifier, decreasing diplomatic reputation even more, though without the influence penalty. The simplest way to deal with this is to forcibly annex Roma, but do it last, immediately before the player intends to use the Rein in Northern Italy decision. Once taken, a one-time event will fire very soon where the Pope asks for Rome back (long before the player has a chance to finish coring it or adding it to the HRE). If it is returned, the malus is removed. So capturing, enacting the decision, and then returning the province avoids the penalties.
Conquest of all of these provinces itself would provide a lot of Aggressive Expansion. Releasing Aquileia from Venice and Urbino from The Papal State and diplo-vasallizing them do not generate any Aggressive Expansion for the player. With a lot of luck separatist rebels can spawn and create cores - Ferrarese in Romagna and Urbinese in Umbria and Ancona. Return of core to HRE member is then AE free and reconquest of vassal's cores generate much less of AE then claim-based conquest. Return of HRE core Brescia from Venice to Milan is not necessary as it is already part of HRE, however returning the province back to HRE will decrease malus in Imperial Authority growth caused by HRE provinces in hands of non-HRE members. Any province can be given in peace deal to an ally too in order to lower AE (e.g. Romagna to Florence or Ferrara) but some luck is necessary then that AI will add the province to HRE.
Ultimately, preventing the Shadow Kingdom event means more Imperial Authority through more princes in the Empire, but it also means more wars to keep minor states in line, and potentially more princes to fall victim to the Reformation spread. Careful management will be needed to ensure that Austria can keep the Italian princes in line with the rest of the Empire. However, it may not be up to you or your ability to keep the Italian Princes in line. If the Burgundian Succession AND Hungary's Automatic Personal Union doesn't fire, the effort to Reign in Italy will allow the Reformation to run rampant in the HRE and will destroy whatever imperial authority you managed to save in Italy.
Burgundy through Personal Unions controls Imperial territory in Holland and Brabant, as well as six Imperial provinces of its own, making thirteen. This is by far the largest drain on monthly Imperial Authority in 1444.
The strategies behind dealing with Burgundy should have in mind keeping Imperial territory in Empire hands and protected from France and England. These strategies can be started from Sundgau via fabrication or a rival conquest mission, but Burgundy and its subjects & ally are a match for all of Austria's power, so the player should bring allies. Ways to pull apart Burgundy include:
- Through the Burgundian Succession Crisis (a luck-based event), which can give direct control over all provinces already in the Holy Roman Empire currently controlled by Burgundy or its subjects. The event's effects are improved if the player has a Royal Marriage with Burgundy and the event is more likely to fire if Burgundy is in a war, and losing. Note though that France will generally receive control of the Bourgogne, Picardie, Artois, Charolais, Nevers, and Rethel provinces. The player can choose to release the princes after inheriting their land for more Imperial Authority; either way, this can form another base of territory in the Empire to keep the princes in line. This method is ideal, since it involves no wars, no costs, and no aggressive expansion, but the event may or may not occur so it cannot be counted on.
- War forcing Burgundy to move their capital to one of their Imperial provinces. This causes Burgundy to become an Imperial prince thus restoring all Imperial provinces to the Empire as well as bringing both Brabant and Holland back into Imperial arms. In recent patches, a country must have no other non-Imperial provinces when their capital is taken in order to move it to Imperial territory. The provinces to remove are thus Picardie and Artois (which can be released together as a vassal), Charolais, and the capital Bourgogne. Additionally, in order to take the last two the player must take Franche-Comté unless other area nearby has already been taken from others such as Savoy or Lorraine. All of this is made much easier (and thus possible with a single war) by having Picardie and Artois already in another nation's hands: France has missions and England generally fabricates claims. If the Burgundian Succession Crisis happens after this, France's only remaining gains will be Nevers's provinces: Nevers & Rethel. This method leaves France weakest, and gives Austria some direct territory, but garners a large amount of aggressive expansion.
- At least two wars, canceling the subjects of Holland & Brabant (ideally done first as this makes further wars easier), releasing Hainaut & Luxembourg, and reclaiming Franche-Comté. If the Burgundian Succession Crisis happens afterward, France generally gains whatever Burgundy has left other than Flanders. This means all 6 normal provinces: Bourgogne, Picardie, Artois, Charolais, Nevers, and Rethel. This method can involve little or no aggressive expansion (depending on what is done with Franche-Comté), which is useful if taking other land nearby. For the player, the effect is almost the same as if the Burgundian Succession Crisis event had happened in their favor, though obviously at the cost of the wars.
Other subject members
Provence at the start is the suzerain of Lorraine (Metz and Lothringen) and controls the Imperial territory of Barrois, from which the player can release Bar to have an extra prince. As this is three Imperial provinces, it's important to handle, but Provence is allied with France to begin. For a super aggressive start, the player can fabricate claims on Lothringen, get a big ally (such as Burgundy or Hungary), wait until France/Provence is at war or just finished one, and then use the claim to declare war. It's possible to damage France, take their money, and even humiliate them for Power Projection if they're a rival. Once France is out of the fight, Provence can be focused. At the start, Provence is just small enough to vassalize, which will also release Lorraine. This causes a bit of aggressive expansion, but will eventually allow the player to annex Provence, getting cores next to France and adding territory to the Empire for a boost to Imperial Authority.
Holstein is also part of the Empire, but is a vassal under Denmark. If Denmark goes to war with the Empire early and loses, it is possible that Holstein may be released, but it is otherwise annexed fairly quickly and thus difficult to get back. It may be advisable to leave this province as the one lost cause, at least until the player is strong enough to handle Denmark.
Territories of non-member nations
Neumark, province of the Empire, starts under Teutonic Order's control at the start. There is an event that can allow the TO to sell Neumark to Brandenburg, but otherwise Brandenburg will usually get it via war. Brescia, a Venetian province, is also part of the Empire, and can usually be returned to Milan should Austria go to war with Venice to add their provinces to the Empire. Do note that since Brescia is already an HRE province, it does not need to be controlled to avoid the Shadow Kingdom event or to use the Rein in Northern Italy decision.
If the first Imperial Reform is passed, the Imperial Ban casus belli may be used to secure these provinces.
Minimizing the Reformation
For the Holy Roman Emperor, the Reformation is effectively an unavoidable disaster that affects the entire Empire. Princes will convert as their provinces are converted, and each prince that does so causes an Imperial Authority growth penalty. Furthermore, any of the player's provinces that get converted (or any converted provinces taken in war) are still very difficult to change back as missionary strength is quite low to start.
The simplest method for handling the Reformation is to use the Emperor diplomacy options to enforce your religion on each prince as they convert. Assuming that they like the Emperor enough or he has enough diplomatic reputation, they will convert back at the cost of a single point of Imperial Authority and some relation points. When this occurs, their capital is immediately converted, and if there was a Center of Reformation in that location, it is removed. Furthermore, the prince will then work to reconvert their own heretic provinces.
This will not work in all cases, however. The Emperor will likely have enemies in the HRE that will refuse the request, and it is not possible to even ask this of Electors. Thus, the second simplest method is going to war with the country (perhaps by attacking their allies, if they are difficult to get a CB upon themselves). For a heretic country, a war option is conversion, which has a higher war score cost depending on how many provinces are of the heretic religion. Successfully enforcing this concession has the same effect as above: their capital is immediately converted, also removing any Center of Reformation there. It can often be worth declaring a no-CB war if required in order to remove a Center.
If a country is too big to convert via war concession, the next option is to take some of the converted provinces, especially a province with a Center of Reformation, with the hope of force-converting in a second war. This can be painful, as the converted provinces will obviously reduce religious unity and will have high unrest, and religious zeal will prevent their conversion until ten years after they were first converted. Centers of Reformation, however, can be reconverted immediately (assuming one has the missionary strength to do so), and as soon as the conversion is complete the Center is removed. For this path, taking the Religious Idea group can be very beneficial if not actually required.
As having a heretic Elector is especially bad, there is one final option: going to war to revoke their Electorate. This carries a whopping ten point penalty to Imperial Authority and some relations penalties with other Electors, but if successful allows the Emperor to choose a new (hopefully loyal) Elector. The no-longer-Elector prince is then able to be converted normally. As the malus is especially egregious, this method is not recommended unless there are no other options.
It is possible for a Center of Reformation to appear in an area that the player cannot or should not do something about. One in Denmark, Spain, or Poland, for example, can be difficult to remove. As long as it is outside the Empire, their conversion of HRE provinces should be slowed and the effects should be infrequent enough to handle without too much difficulty. Still, taking said Center or making them change it should be added to the list of priorities for some future date.
One way to reduce the impact of the Reformation is by acting before it occurs. Let single-province countries like Friesland or Oldenburg be annexed by larger countries to prevent Centers of Reformation and religious rebels from instantly converting these princes. This decreases Imperial Authority tick, as there are fewer princes, but they may be released after 1650 if their cores still exist. With the above methods this may be unnecessary, but it can still be helpful, especially if one has not yet had the chance to take the Religious Idea group or chooses not to do so.
If the player wishes to convert to Protestantism themselves, it must be noted is that an election will be triggered if the player is the emperor. The player will not be eligible to be emperor again until a Holy War has been won or tied (Peace of Westphalia). This conversion path would only make strategic sense if the Reformation has been very successful, the player already is struggling with low religious unity and/or the player has already lost the throne (especially to a weak nation that is more likely to lose a Holy War). Being Protestant does give a +15% relations benefit, which is helpful for an emperor.
Another strategy is to intentionally allow Italy to leave during the Shadow Kingdom Event. This allows you to ensure early Personal Unions over Bohemia and Hungary, and to force Burgundy to release HRE provinces back into the HRE. Finally, your extra time can be spent gaining small chunks territory in Northern Germany that would allow to claim a province of protests princes and force convert them. While this is not ideal, remember that heretic princes will be more of a threat to Imperial Authority than the amount of princes in the HRE. Finally this strategy allows you to better manage the HRE over the long run.
Growing the Empire
As the likely end goal for Austria is to unite the Empire into a single nation and this is done without all the usual diplomatic monarch point expenditure of diplo-annexing, a strong late game goal is to grow the HRE. One easy way to do this is to revive peripheral nations with cores outside the realm. The Teutonic Order is often swallowed whole by Poland/Commonwealth. It can easily be freed from Brandenburg in one of the typical wars necessary to free captured duchies and then an Imperial Liberation CB can be used on Poland to take back Prussian provinces.
Similarly, Burgundy's capital is often driven by France into its provinces within the HRE, making it a member. At this point, Imperial Liberation can be used to reclaim Burgundy.
Since nations on the periphery of the Empire are typically threatened by a strong France, Commonwealth or Scandinavia, they typically add captured provinces to the Empire if they have good relations with the emperor. This makes them good allies or vassals if the emperor is strong and has the empire under control enough to take on the big neighbors.
Diplomatic or Influence are strong contenders for first idea group due to the importance of holding onto the Holy Roman Emperor title. Both grant an +1 diplomatic relations and +2 diplomatic reputation (+10 modifier for elections and +5 per point for supporting Empire reforms). Influence enables reduced diplomatic annexation costs (−25%). Diplomacy, however, may have better events (including one that could give +5 Imperial Authority), better improved relations (+25%), and free royal marriage breaking (from −1 stability to −1 prestige).
Offensive or Defensive are both helpful to Austria as a major land power that must repel hostile invasions on the HRE. Offensive may be slightly more useful due to the need to wage many small wars within the HRE to free annexed states, as Engineer Corps decreases the length of siege times +20% and Grand Army provides a larger force limit +20% to win battles against the French, Ottoman or Polish armies.
Religious or Humanism may be essential by the third idea group in order to counter the heretics during the Reformation. It is in the Emperor's interest to remain Catholic and convert Protestant/Reformed princes back to Catholicism which makes Religious a strong choice. However, if the Reformation starts right next to or within Austria, Humanism may be necessary to prevent the religious turmoil disaster. Alternatively, the Religious-Offensive policy (Anti-Heresy Act) offers a powerful bonus (+20% Religious Unity, +3% Missionary Strength vs Heretic) for a −1 monarch point upkeep cost.
Afterwards for the fourth or fifth idea group, take exploration and expansion if you wish to get AEIOU, it is in the mission tree to have holdings in India and China and have all of Australia. also, you might have gotten the Burgundian lowlands under direct control(through the Burgundian Succession event) or Iberia under a PU(through Spain, a Habsburg throne event). if you like colonial games, then it will be very good to colonize if you have the lowlands and Iberia and become OP and rich. otherwise, just ignore colonization as it won't be worth it.