Replenish
From The Unofficial Bad North Wiki
Units can be replenished inside houses or churches, refilling the slots of fallen soldiers.
The action can be started by clicking on a unit, clicking the replenish button and choosing an empty and undestroyed house or church on the map.
If the replenishing action is interrupted for any reason (e.g. the building is destroyed), the amount of replenished soldiers will depend on the amount of time passed. A small, colored wheel appears during a replenishment above the building, indicating how much time is left until the action is complete and how many soldiers are currently replenished.