PAM was mobilized on a number of occasions in the latter half of the 19th century, including the Fenian raids, the Wolseley expedition, the North-West Rebellion, and the Second Boer War.

The Second Boer War saw more than 8,000 volunteers raised for service in South Africa, from a number of militia regiments in Canada, including PAM.

[7] As World War I drew to a close in 1918, and the CEF expected to disband, plans to re-organize the Canadian Militia were initiated under the Otter Commission.

[9] Following the results of the Otter Commission, two more infantry regiments were integrated into PAM, 22nd Battalion (French Canadian) of the CEF (later renamed the Royal 22nd Regiment), and Princess Patricia's Canadian Light Infantry.

[12] In the Interwar period, PAM was occasionally mobilized in order to maintain "peace," between strikers and business owners during strikes.

[12] At the outbreak of World War II in 1939, PAM fielded a force of 455 officers, and 3,714 soldiers of all other ranks.