The Battle of the Atlantic was the longest battle of the Second World War and was fought at sea from 1939 to 1945.
Much of the burden of fighting the battle fell to the RCN which, at the outbreak of the war,
was comprised of only six destroyers and a handful of smaller vessels.

Over the course of 2,075 days Allied naval and air forces fought more than 100 convoy battles
and performed as many as 1,000 single ship actions against submarines and warships of the German and Italian navies.
Primary targets for the Germans and Italians were the convoys of merchant ships carrying vital,
life-sustaining cargo from North America to Europe.

Canada’s navy was instrumental in turning the tide of the war,
and by the conflict’s conclusion had grown to become one of the largest in the world.
The RCN destroyed or shared in the destruction of 33 U-Boats and 42 enemy surface craft.
In turn, it suffered 2,210 fatalities, including nine women, and lost 33 vessels.

For more information see the link below.

https://www.canada.ca/en/navy/corporate/history-heritage/battle-atlantic/1939-1945.html