1943
Canadian military intelligence and the Royal Canadian Mounted Police (RCMP) intercepted mail addressed to several Kriegsmarine officers (including Otto Kretschmer) imprisoned at the Camp 30 prisoner of war camp at Bowmanville, Ontario in early 1943. The correspondence detailed an escape plan where the prisoners were to tunnel out of the camp and make their way (using currency and false documents provided for them), through eastern Ontario and across Quebec to the northeastern tip of New Brunswick off the Pointe de Maisonnette lighthouse where the escapees would be retrieved by a U-boat.
Canadian authorities did not tip off the POWs and detected signs of tunnel digging at Camp 30. All prisoners except one were arrested at the time of their escape attempt; the sole inmate who managed to escape travelled all the way to Pointe de Maisonette undetected, likely travelling onboard Canadian National Railway passenger trains to the Bathurst area. This POW was apprehended by military police and RCMP on the beach in front of the lighthouse on the night of the planned U-boat extraction.
The RCN provided a U-boat counter-offensive force (code-named "Operation Pointe Maisonnette") that was led by HMCS Rimouski (a flower-class corvette), which was outfitted with an experimental version of diffuse lighting camouflage for the operation.
The task force led by Rimouski waited in Caraquet Harbour, obscured by Caraquet Island, the night of 26–27 September 1943 and detected the presence of U-536 off Pointe de Maisonnette while shore authorities arrested the POW escapee.
U-536 managed to elude the RCN task force by diving just as the surface warships began attacking with depth charges; the submarine was able to escape the Gulf of St. Lawrence without making the extraction.
Read more about this topic: Battle Of The St. Lawrence