From 13 January 1942, Dönitz planned to begin a surprise offensive from the Gulf of Saint Lawrence to Cape Hatteras. Unknown to him, ULTRA had read his Enigma signals and knew the position, size, and intentions of his boats, down to the date the operation was scheduled to begin. The attacks, when they came, were not a surprise. Of the 12 U-boats that began the offensive from the Grand Banks southward, just two survived the war. The operation began the Battle of the St. Lawrence, a series of battles which lasted into 1944. It remained possible for a U-boat to operate in the Gulf into 1944, but countermeasures were strong. In 1942, the global ratio of ships-to-U-boats sunk in Canadian waters was 112:1. The global average was 10.3:1. The solitary kill was achieved by the RCAF. Canadian operations, as with American efforts, were a failure during this year.