On the first day of May, 1945, The Third Reich was in the final stages of its collapse. Adolph Hitler was dead and Grossadmiral Karl Donitz had been named as his successor. At the time of his appointment, Donitz was also the head of the entire German navy (Kriegsmarine) which had close to 400 U-Boats in operation or close to operation, of which sixty-two were actually at sea. Unlike the soldiers of the Wehrmacht who were largely disorganized and seeking only to avoid capture by Soviet troops, the men of the Kriegsmarine were unbroken, loyal to the Reich and confident in victory. So it was with some shock that the captains and crews of the German U-boat fleet received Donitz’s orders on May 4: “All U-boats cease fire at once. Stop all hostile action against allied shipping. Donitz.” The end of the Reich was imminent and it came as a shock to Germany’s submariners who had believed the fantastic rhetoric of imminent German successes that had been fed to them only a few days earlier. In Black Flag: The Surrender of Germany’s U-Boat Forces (Zenith Press, August 2009; 196 pages) Lawrence Paterson presents the complete story of the final days of the U-Boats and how their surrender was accomplished. Although Donitz called on his U-boats to surrender on May 4, several did not immediately heed his command. The commanders of other U-boats elected to scuttle their craft rather than allow them to fall into Allied hands. Still other U-boat crews accepted their fate and proceeded to the nearest Allied port to surrender. Black Flag presents the story of each U-boat that was at sea on May 4 and of the men who manned them. Patterson’s research has been thorough and meticulous. He reports on the experiences of dozens of U-boats and what they experienced at the time they were surrendered and of whether their crews were well treated or abused. For example, Paterson tells the story U977, commanded by Oberleutnant zur See Heinz Schaffer, eluded capture for more than two months until it finally surrendered to Argentine naval authorities on August 17, 1945. U977 had been in North Atlantic waters when the order to surrender was received. After setting eighteen crewmembers ashore in Europe, U977 and thirty remaining submariners set off on an odyssey that would keep them beneath the surface of the ocean for more than two months and take them all the way to Argentina. Paterson also addresses the destruction of the German U-boat fleet following the war and the disposition of the few U-boats that were not scuttled. He considers the post-war approach to U-boats that Churchill, Truman and Stalin discussed at the Potsdam conference and the decisions made with respect to U-boats by the Tri-Partite Naval Commission. He describes how certain U-boats were destroyed and offers the location of the four remaining U-boats that have survived. Black Flag includes many useful features that make reading much easier, including a practical glossary and a table of comparative rank table that explains how German military ranks compare to American and British ranks. Paterson has well-footnoted his work and provided detailed appendices which include identification of all U-boats at sea on May 4, 1945, the full text of Donitz’s surrender instructions and a list of the U-boats scuttled after the war. In addition, Black Flag offers a thorough bibliography and an excellent index. Black Flag: The Surrender of Germany’s U-Boat Forces is a very readable account of the final days of Germany’s U-Boat fleet and students of the Kriegsmarine and submarine warfare, in general, will certainly want to add it to their collections. Novice readers, however, may find the level of detail overwhelming and should consider developing a stronger knowledge base before delving into this excellent study of the surrender of the undefeated German submarine navy as World War II drew to a close.