Gambit is a new combat action introduced in Fire Emblem: Three Houses.
Gambits are special tactics units can perform dependent on their assigned battalion. Some gambits are used for offense, while others are used for support. Each gambit has a defined area of effect, with many gambits targeting more than one map tile at once. The strength of a gambit is affected by the unit's Charm. Each gambit has a set number of uses per battle determined by the unit's Authority. If a unit's battalion takes too much damage and runs out of stamina, its gambits can not be used. Enemy units are also capable of deploying gambits against the player's force.
Depending on the offensive gambit deployed, a variety of effects may occur in addition to damage inflicted. Such effects include temporarily spreading damaging fire on tiles within the area of effect, poisoning the enemy, or shifting the enemy's position by pushing them away or drawing them to the attacking unit's rear. Human enemies struck by gambits temporarily lose the ability to move, but can still act on their following turn.
When fighting giant enemies such as demonic beasts, gambits can be used to damage and shatter the beast's shield tiles. Targeting a beast with a gambit will also draw the beast's aggro toward the unit that used the gambit.
When a gambit is used on an enemy within the attack range of one or more of your allied units, it will become a Gambit Boost which increases the might (Mt) and hit rate of the gambit. This boost will increase based on the number of participating units and their respective support levels to the user.