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, known as Operation Kiebitz, in which the prisoners were to tunnel out of the camp and make their way (using currency and false documents provided to them) through eastern Ontario and across Quebec to the northeastern tip of New Brunswick off the Pointe Maisonnette lighthouse where the POW 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 shortly afterward.

This POW was apprehended by military police and RCMP on the beach in front of the lighthouse the night of the arranged U-boat extraction.

U-536 managed to elude the RCN task force by diving just as the surface warships began attacking with depth charges; however, the submarine was able to escape the Gulf of St. Lawrence without making the planned extraction.