At 13.17 hours on 9 March 1942 the unescorted and unarmed Hanseat (Master Einar E.V. Brandt) was hit by two torpedoes from U-126 10 miles north-northeast of Cape Maysi, Cuba. The first torpedo struck on the starboard side in the bow and tore holes in both sides, the second hit simultaneously in the stern, just ahead of the propeller near the engine room. The tanker immediately settled by the stern, due to the flooding of the engine room. The engines were stopped and distress signals were sent, before the Danish crew abandoned ship in all four lifeboats. A short time later, the U-boat surfaced and started to shell the Hanseat for about two hours. About 200 rounds were fired into the port side, setting the tanker ablaze.

One lifeboat had an outboard motor and reached the village of Maysi about seven hours after the attack. The men in the boat immediately left aboard the Cuban motor launch Corsario to rescue the other survivors. In the meantime, the men in the remaining lifeboats sighted the Panamanian motor tanker Pheobus (Master Hans K. Groth), en route from New York to Caripito, bearing directly toward the burning Hanseat. Brandt hoisted a yellow flag to warn her, because they were only 7 miles away from the wreck and they thought that the U-boat was still in the vicinity. The other tanker came near and Groth spoke to Brandt, inquiring him about the condition of the survivors and offering assistance. Brandt told him to keep on going in order not to endanger his ship by stopping. Groth promised to send help and proceeded on his course. By this time the last sign of smoke from the Hanseat had disappeared, apparently the ship was completely sunk. Two hours after leaving Maysi, the motor launch arrived at the scene and took the three lifeboats in tow to Maysi. The survivors were then transported on the Corsario to Baracoa, Cuba and later by bus to Havana. They were flown to Miami and were then sent by train back to New York, arriving on 24 March.