On 16 Feb 1942, U-156 commenced Operation Neuland with an attack on Aruba in the Caribbean. Around 08.00 hours, the U-boat attacked two tankers lying at anchor in the roads of San Nicholas harbour, hitting Pedernales and Oranjestad. At 08.11 hours, U-156 began to shell the Lago oil refinery at San Nicholas, but the crew of the deck gun forgot to remove the water plug from the barrel, causing an explosion that seriously wounded two men*. 16 rounds from the 37mm AA gun were fired, but only two hits could be located by the Allies: a dent in an oil storage tank and a hole in a house.
The U-boat then continued towards Oranjestad harbour and at 09.43 hours torpedoed the Arkansas lying at the pier of the Eagle Refinery, after missing with two torpedoes.

The Pedernales (Master Herbert McCall) was hit amidships by one G7a torpedo and burned fiercely all night, but did not sink. The next day tug boats pushed her ashore near Sabaneta and she was later taken to the Lago Dry Dock in San Nicholas, where the midship section was removed, the bow and part welded together and a temporary wheel house fitted. The tanker went to Baltimore under her own power and returned to service after being rebuild.

* Matrosengefreiter Heinrich Büssinger died of wounds within one hour and was buried at sea the next day. The gunnery officer (II WO) Leutnant zur See Dietrich von dem Borne lost his right foot and a lot of blood, so Hartenstein got permission from the BdU to put him ashore into French captivity at Fort de France, Martinique on 21 February. On 26 February, after using up all torpedoes, the commander decided to saw off the ruined portion of the gun barrel and used this shortened gun to sink two more ships.