The strategic logic was straightforward and devastating. Britain needed four tanker loads of petroleum per day to sustain its war effort, and after Italy blocked the Mediterranean route from the Middle East, most of that oil came from Venezuela's fields through the refineries of the Dutch Caribbean. The Royal Dutch Shell refinery on Curacao, processing eleven million barrels per month, was the largest in the world. The Lago refinery on Aruba and the Pointe-a-Pierre refinery on Trinidad -- the largest in the British Empire -- completed the triangle. Beyond oil, the United States depended on bauxite shipped from the Guianas along routes paralleling the Lesser Antilles to produce the aluminum that built its warplanes. Disrupt these lanes, and the Allies would feel the pain in factories, airfields, and fuel depots across two continents. The Caribbean, so often imagined as a place of leisure, was in fact an industrial artery -- and in early 1942, it was almost entirely undefended.

Six German U-boats and five large Italian submarines sailed from ports in France in January 1942, briefed by former Hamburg America Line captains who knew Caribbean waters from peacetime service. The first three U-boats -- U-156, U-67, and U-502 -- had orders to strike simultaneously on the night of February 16. Off Aruba, Werner Hartenstein's U-156 torpedoed the tankers Pedernales and Oranjestad at anchor outside San Nicolaas, then moved within half a mile of the Lago refinery to shell it with the deck gun. A crewman had forgotten to remove the tampion from the muzzle. The first shell detonated in the barrel, killing one gunner and splaying the muzzle open. At Curacao's Willemstad harbor, U-67 launched six torpedoes at three anchored tankers; four hit their targets but failed to explode, and only the stern tubes found success. U-502 ambushed the Lake Maracaibo tankers offshore. Roughly ten percent of those small vessels were destroyed on the first day. For the merchant sailors aboard -- Venezuelan, Chinese, Dutch, and others working the oil routes -- the war had arrived without warning in waters they had considered safe.

Two days later, U-161 under Albrecht Achilles attempted something few submarine commanders dared. Achilles and his first watch officer had both visited Trinidad's Gulf of Paria as Hamburg America Line employees before the war. They knew the harbor. U-161 entered through a narrow, deep passage at periscope depth in broad daylight on February 18. An electronic detection system registered the submarine's passage at 9:30 that morning, but the signal was dismissed as a patrol boat. After spending the day resting on the harbor floor, U-161 surfaced after dark, torpedoed two anchored ships, then exited the gulf with decks awash and running lights on, mimicking a harbor craft. Achilles returned weeks later to Castries harbor in Saint Lucia, entering the shallow, narrow entrance on the surface using electric motors. He torpedoed two freighters that had just arrived carrying supplies to build a new American base, then raced out under machine gun fire. The harbor, previously considered immune to submarine attack, was fitted with an anti-submarine net afterward.

The human toll fell hardest on merchant sailors -- the tanker crews, the freighter hands, the refinery workers caught in the crossfire. Four Dutch marines died attempting to disarm a beached torpedo on Aruba the day after the initial attack. The Chinese crews imprisoned for refusing to sail without protection were eventually released when escort arrangements could be made, but refinery output had already declined. The Allies, scrambling to respond, broadcast suggested routes for unescorted merchant ships. The U-boats intercepted the broadcasts and were waiting at the suggested locations. U-129, patrolling southeast of Trinidad, intercepted bauxite freighters along these radioed routes, briefly halting the aluminum supply chain. By the time the submarines turned for home, Operation Neuland had demonstrated how vulnerable the Caribbean's oil and mineral infrastructure was. Coastal artillery, aircraft patrols, and submarine chasers gradually made the region less hospitable for U-boats, and the element of surprise could not be repeated. But for the merchant mariners who worked these waters in early 1942, the Caribbean had become as dangerous as the North Atlantic.