At 07.16 hours on 28 November 1942 the unescorted Alaskan (Master Edwin Earle Greenlaw) maintained a zigzag course in heavy rain, as one of the lookouts spotted the wakes of two torpedoes from U-172. One torpedo missed and the other struck the ship amidships on port side. The explosion destroyed the main engines, both port side lifeboats, knocked down both aerial antennas and the topmast. It also buckled the deck, destroying the deck gear and machinery. The Alaskan quickly listed to port but did not sink. 10 officers, 32 men and 16 armed guards (the ship was armed with one 5in, one 3in, four 20mm and two .30cal guns) were ordered to leave the ship 25 minutes after the attack. The #3 lifeboat swamped on launch and this forced the survivors to abandon ship in the overcrowded last intact lifeboat or jump overboard and swim to rafts and floats. Then U-172 surfaced and shelled the ship at the rate of one shot a minute. She fired about 60 rounds, hitting the ship about 40 times, until the burning Alaskan rolled over and sank bow first at 08.10 hours about 800 miles northeast of Natal, Brazil.

The lifeboat #1 was launched with 22 crew members and 11 armed guards and pulled away from the ship. Four crew members died of injuries or exposure in this boat and were buried at sea before it made landfall at Salinas, Brazil on 15 December, where one of the armed guard died in a hospital and was buried there. 11 crew members and three armed guards managed to reach a large raft, but one crewman died of injuries shortly afterwards and was buried at sea. The survivors were picked up by the Spanish steam merchant Cilurnum on 13 December and were brought to Las Palmas, Canary Islands. They stayed there for 25 days before going on to Cadiz and were eventually repatriated via Gibraltar.

The master, the armed guard commander, the second mate, the radio operator, one armed guard and four crew members rescued themselves on another raft. U-172 came alongside and took the master aboard. After asking the usual questions, Emmermann told him: Sorry we sank you, but this is war. Why don’t you tell America to get out of the war., before he was allowed to go back to the raft. On the next day, they righted the swamped lifeboat #3 and transferred into it. They spent 39 days at sea before reaching land after a voyage of about 2000 miles south of Cayenne, French Guiana on 5 January 1943. They followed the coast until they reached Cayenne and made landfall safely with the help from a fishing boat. All were hospitalized and treated well by the local government officals. A few days later they were moved out of French Guiana by aircraft. In all, two officers, four men and one armed guard lost their lives.