Information for this posting comes from an excellent article by Thomas Foster, "Postal History of the Canadian Forces in Jamaica, 1940-46" published in Stamp Collecting, October 22, 1965.
Readers may be interested in this 1984 article in Topics.
In 1940, British forces in Jamaica were withdrawn to Britain. Canadian troops known as the "Y" force were sent to replace those troops and took over the British bases.
Since the Canadians did not have their own postal facilities, mail posted at the Camp Post Office was taken to the Jamaican post office for conveyance. Mail required Jamaican postage stamps.
According to Foster, the first postage rates were 1s. per oz. airmail letters to Canada and 2 1/2d. for surface letters. By May 17, 1942, the air mail rate to Canada was 6d per oz.
All letters were handstamped with a "Y" Force Military Censor marking.
Battalions Serving in Jamaica
1) Winnipeg Grenadiers (May 30, 1940 - September 13, 1941)
The first Canadian battalion serving in Jamaica were the Winnipeg Grenadiers. After their service in Jamaica, the Grenadiers were transferred to Hong Kong where they faced Japanese forces in the Battle of Hong Kong.
Kingston to Birmingham, Alabama, June 17, 1940
2) 1st Batallion, Argyle and Sutherland Highlanders of Canada (September 10, 1941 - May 20, 1943)
Argyle and Sutherland Highlanders Orderly Room handstamp, September 30, 1942, to Hamilton
An example of a scarce "free" surface cover
|"Y" Force censor No. 6|
3) Irish Fusiliers of Canada (Vancouver Regiment) (May 18, 1943- August 6, 1944)
Kingston, to Terrace B.C., October 4, 1943
Air mail post card
4) Brockville Rifles (August 5, 1944 - February, 1946)
Kingston to Toronto (Received October 20, 1944)