In the 1700s, Häme Castle served as a base for Swedish troops and as a military storage facility. The main activities were concentrated in the new surrounding perimeter wall buildings, which housed soldiers and the Crown Bakery, capable of producing large quantities of bread for the army.

The main castle was used as a grain storage facility for the military. During the Great Northern War (1700–1721), when the Russians occupied the castle, the great hall was used as a stable for horses. In the 1720s, the four-tower castle was transformed into a two-tower structure as new storage rooms were built between the towers and the third-floor defensive corridors, creating a unified third floor.