Operation Drumbeat is the story of Germany's first deliberate attacks against the United States in World War II. The attacks took the form of torpedo launchings, and deck-gun actions by submarines, called U-boats, against American and Allied freighters and tankers steaming with war cargoes along the U.S. Atlantic Coast, in the Caribbean, and across the Gulf of Mexico during the first eight months of 1942.

By August, the number of sinkings reached nearly 400, with loss of over 5,000 U.S. and Allied merchant seamen and sailors-twice the number of fatal casualties at Pearl Harbor the preceding December. In his magisterial work A World at Arms (1994), historian Gerhard L. Weinberg called the offshore battle"the most disastrous defeat ever suffered by American naval power," and credited this book as "a major study of the whole disaster."