The Canadian Expeditionary Force (CEF) was the army raised by Canada for overseas service during World War I. In August 1914 Britain accepted the Canadian offer of an expeditionary force initially fixed at a strength of 25,000. However, the first contingent, which sailed for England in October 1914, actually comprised 31,000 men, many of them British-born. The size of the force increased steadily, with the 1st Canadian Division being sent to France in early 1915. Later that year a Canadian corps of two divisions was formed there, reaching its full strength (four divisions) in 1916. A fifth division, formed in England, was not sent to the Western Front except for its divisional artillery and a number of specialist units. It was thought that providing reinforcements for this last division would be problematic.
Stacey, C.P. "Canadian Expeditionary Force", The Canadian Encyclopedia. Retrieved on 28 August 2008.