Perhaps the most decisive battle of WW II took place in the North Atlantic in 1943. At this time the German U-boat fleet was at its strongest, while American shipbuilding was producing more ships (six a day) than could be crewed by experienced seamen. Britain was under blockade but the Allies looked forward to the invasion of Europe in 1944, a move that could not take place without the massive transfer of materiel from the States to England. Sonar was in its infancy and U-boats shadowing the convoys would have clear shooting--had not the Allies broken the German code and known every action the wolf packs were planning. Nonetheless, our losses were horrifying to the few who had full knowledge. Even Churchill was ""frightened."" Convoy follows one voyage east in March 1943, letting it stand for hundreds of others. The eyewitness accounts, both German and Allied, have a humanity that is richer than most such recitals; the interviewees respond to Middlebrook with a spontaneity beyond mere facts. Steady on the strategy, gripping in distress.