The United States during World War II was unprepared for one of Germany's most destructive war efforts: a U-boat assault on Allied ships in the Caribbean that sank about 400 tankers and merchant ships, with few losses to the German submarine fleet. The Germans had set up a network of spies and had the secret support of some dictators, including the Dominican Republic's Rafael Trujillo, supplying their U-boats with fuel.The Caribbean was of crucial strategic importance to the Allies. Roughly 95 percent of the oil sustaining the East Coast of the United States came from the region, along with bauxite, required to manufacture airplanes. The United States invested billions of dollars to build bases, landing strips, roads, and other military infrastructure on the Puerto Rico and secured a 99-year lease on all the British bases located in the Caribbean. The United States also struck an agreement with neutral Vichy France to keep the French Navy in the harbor of Martinique, preventing it from being turned over to the Germans, in exchange for a food supply for the island. Elsewhere, however, the German blockade was taking a dire human toll. All of the islands experienced a drastic food shortage. The US military buildup created jobs and income, but locals were paid a third as much as continental workers. The military also brought its segregationist policies to the islands, creating further tensions and resentment. The sacrifice of the Caribbean people was bitter, but their participation in the war effort was also decisive: The U-boat menace more or less disappeared from the region in late 1943, thanks to their work building up the US military operation.

The United States during World War II was unprepared for one of Germany's most destructive war efforts: a U-boat assault on Allied ships in the Caribbean that sank about 400 tankers and merchant ships, with few losses to the German submarine fleet. The Germans had set up a network of spies and had the secret support of some dictators, including the Dominican Republic's Rafael Trujillo, supplying their U-boats with fuel.The Caribbean was of crucial strategic importance to the Allies. Roughly 95 percent of the oil sustaining the East Coast of the United States came from the region, along with bauxite, required to manufacture airplanes. The United States invested billions of dollars to build bases, landing strips, roads, and other military infrastructure on the Puerto Rico and secured a 99-year lease on all the British bases located in the Caribbean. The United States also struck an agreement with neutral Vichy France to keep the French Navy in the harbor of Martinique, preventing it from being turned over to the Germans, in exchange for a food supply for the island. Elsewhere, however, the German blockade was taking a dire human toll. All of the islands experienced a drastic food shortage. The US military buildup created jobs and income, but locals were paid a third as much as continental workers. The military also brought its segregationist policies to the islands, creating further tensions and resentment. The sacrifice of the Caribbean people was bitter, but their participation in the war effort was also decisive: The U-boat menace more or less disappeared from the region in late 1943, thanks to their work building up the US military operation.

Despite Puerto Rico being the hub of the United States' naval response to the German blockade of the Caribbean, there is very little published scholarship on the island's heavy involvement in the global conflict of World War II. Recently, a new generation of scholars has been compiling interdisciplinary research with fresh insights about the profound wartime changes, which in turn generated conditions for the rapid economic, social, and political development of postwar Puerto Rico. The island's subsequent transformation cannot be adequately grasped without tracing its roots to the war years. Island at War brings together outstanding new research on Puerto Rico and makes it accessible in English. It covers ten distinct topics written by nine distinguished scholars from the Caribbean and beyond. Contributors include experts in the fields of history, political science, sociology, literature, journalism, communications, and engineering. Topics include US strategic debate and war planning for the Caribbean on the eve of World War II, Puerto Rico as the headquarters of the Caribbean Sea frontier, war and political transition in Puerto Rico, the war economy of Puerto Rico, the German blockade of the Caribbean in 1942, and the story of a Puerto Rican officer in the Second World War and Korea. With these essays and others, Island at War represents the cutting edge of scholarship on the role of Puerto Rico and the Caribbean in World War II and its aftermath.