How many armies can you deploy at once in Game of Thrones: Dragonfire?

You can field up to 5 armies at the same time. Each one is 3 dragons plus 1 troop type.

The number of army slots is unlocked through the Army Expansion research (War Tactics). Until you have them all, you attack with fewer armies.

Building advice: keep your 5 slots always full, and prepare a fixed set of armies rather than improvising every fight. A good set looks like:

• 2 or 3 "long / combo" armies built to last 10 rounds and stack debuffs.
• 1 or 2 "burst" armies to finish a small target fast.

Why several armies: against a full defender, one army is NEVER enough to empty it (see attrition). You have to chain the waves — and having 5 armies ready is exactly that.