Due to the British involvement in the Crimean War, a substantial number of British troops were withdrawn from British North America. By the spring of 1855, only 1,887 British troops remained in Canada, and a further 1,397 were stationed in the colonies of Nova Scotia, New Brunswick, Prince Edward Island, and Newfoundland. As a result, a commission was appointed to examine and recommend measures for the reorganization the Canadian militia.
The consequent Militia Act provided for an active militia force of approximately 5,000 men enlisted on a voluntary basis. The force would include 16 troops of cavalry, 7 field batteries, 5 companies of artillery, and 50 companies of riflemen. In addition, arms and ammunition were to be acquired sufficient to equip 100,000 men in the event that additional militia units were raised. Under the 1855 Militia Act, the volunteer system became a basic element of Canadian defence policy.
The militia staff was comprised of an adjutant-general and two deputy adjutants-general for Canada East and Canada West.
