The White Company
For The White Company achievement the player must have their army fight on both sides of a war. (Just offering the Condottieri and not fighting is not sufficient for the achievement). The achievement name is a reference to the medieval White Company of mercenaries (their leader, John Hawkwood, is represented on the icon).
One method of getting this achievement is to play as Pomerania and join both sides of any conflict between Poland and the Teutonic Order. Note that the Teutonic Order will need to have not rivalled Pomerania or they will be unwilling to accept the offer of Condottieri. Ask for military access across to Fyn from Denmark, and blockade the strait against Poland, this will prevent them for being able to engage Pomerania's relatively smaller army. Once the 18 month timer on the offer Condottieri is over, recall the army, offer it to the Teutonic order, and make sure to fight in a battle against Pomerania's former 'ally'.
Another method is to rent out an army to an attacker in a war, and then form an alliance with the defender. Accept the call to arms and you will get the achievement. For example, play as Byzantium. At the start of the game, offer Condottieri to Ottomans (If Ottoman rival you, restart the game) and start improving relations with Albania. When Ottoman declares war on Albania (If not, just restart the game), offer alliance to Albania, accept the call to arms and the achievement will pop up.
In any game you play, find a nation that you can ally who is currently at war. Offer Condottieri to their enemy (for free even, doesn't matter). After the enemy accepts, send alliance offer to the opposing side whom you rented your army. Once alliance is accepted, they will probably send you a call to arms. Accept it and you will get the achievement. If they do not send a call to arms, you may use enforce peace to the enemy if the enemy will not accept it. There is no need to fight any battles. Another way to easily get the achievement is whenever you are called into a war by an ally, see if any of their enemies would accept condottieri. Offer them the condottieri then accept the call to arms.
Achievement does not work if you declare war on the nation that you rented Condottieri to. You have to actually join an existing war.
- I.e., the player’s country has the flag white_company.