 Before the building of the fort, Inverlochy was the main settlement in the area and was also where two battles took place—the first Battle of Inverlochy in 1431 and the second Battle of Inverlochy in 1645.The town grew in size as a settlement when the fort was constructed to control the population after Oliver Cromwell's invasion during the Wars of the Three Kingdoms, and then to suppress the Jacobite uprisings of the 18th century.In the Jacobite rising of 1745 known as the Forty-Five, Fort William was besieged for two weeks by the Jacobites, from 20 March to 3 April 1746.