I am first pointing to FAQ, in official announcements, flare will add extra knowledge there. Here it is
Now I am going to give you some guidelines. Players can only participate in one war at a time (unless you are assigned as guardian of a watchtower). Realize what this means. That means when you participate in an ongoing war, you can’t help in another war. That means, you have to chose whether you join a war or not. It’s strategy, you have to realize that more wars can be started, so keep some players in reserve to anticipate.
So with that in mind, be smart and don’t join an ongoing war that you can’t change at all. Only join when it’s an important war to win and you can change the outcome. So when you can score a supreme victory, it could be wise to join. Having said that, once you join a war, you make a move and immediately this results in a cool down period, so even when you win, it takes time before you can join another war.
Say, you lose the war. Your hero will lose all it’s troops and be returned to headquarters. So this is also important to realize, when you can’t change the tide, don’t join that war, your troops will be lost and you lose time and energy moving on the map!
Even more important is starting ‘luring’ opponent wars for distraction. Say you plan to destroy a watchtower at a very important place. You can send a player to an unimportant place and declare war there, with objective to lure in a lot of other players from the other team. Since they can’t leave that war, make sure to sacrifice just enough players to prevent a supreme victory and destroy that watchtower with enough remaining forces, when you see that your strategy worked and the other team will not have enough players to prevent your real intention.
So also when two other teams are in a close war, with plenty of time remaining, you can take advantage of this strategy by overwhelming them, players in a war can’t prevent it.
Now about troops, you assign troops on watchtowers and players. Troops can not be assigned on towers and players participating a war. So it’s important to assign those troops before a war is started. They seem to give bonuses in defense and offense. Beware… When a war is lost, those troops are lost completely. Even some troops from victor will be lost.
A player can not participate in an ongoing conquest when he joins an already started conquest. However… he can donate resources. So if you leave one account open, you can use that for adding resources more fast by multiple accounts in reserve indeed.
Also raiding with skull gear is important, wars work just like wars during war season. Only you can only fight in one war at a time (unless being assigned guardian)