After the American civil war, between 1868 and 1871, the Fenian Brotherhood mounted a number of raids into Canada. The Brotherhood was composed mainly of Irish-American veterans, and the goal of the raids was to hold Canada hostage and force Great Britain to give Ireland its independence.
The fear of Fenian raids lasted for decades. In 1886, when the Canadian Pacific Railway laid the last track, England stationed several large warships in the Vancouver harbour to prevent marring of the celebration by the Fenians. The fear had mostly dissipated by the 1890s, when support for the raids collapsed.
It is important to note that a number of key Canadian government officials and political figures lived through those events and served in militia units called out to repulse the raids. Major-General Sam Hughes served with the 45th West Durham Battalion that saw action in 1868. Sir Wilfrid Laurier in 1870 was a lieutenant with the Arthabaskaville Infantry and was awarded the Canadian General Service Medal for his service during the Fenian Raids.
Based on the Fenian raids experience, there was great concern in Canada that German sympathizers, supported by German attachés Captains von Papen and Boy-Ed, would emulate the Fenians and mount raids into Canada to disrupt Canada’s war effort. In actual fact, such raids were planned but were discarded by the German plotters due to the fear of American reaction to such attacks launched from American soil.
While there were some minor incidents, American and Canadian security and border surveillance along the border made these fears mostly unfounded.
Fenians Raids - The Canadian Encyclopedia
Fenian Raids - WarMuseum.ca - A Chronology of Canadian Military History - 1841-1871
Fenian Raids - Wikipedia, the free encyclopedia
Canadian General Service Medal - Veterans Affairs Canada
Anti-German sentiment - Wikipedia, the free encyclopedia
Bartholomew, Robert (1998) Phantom German Air Raids on Canada: War Hysteria in Quebec and Ontario during the First World War, Canadian Military History: Vol. 7: Iss. 4, Article 3.