The Tizard Mission was one of the key events in the forging of the Anglo-American alliance in World War II. Led by Sir Henry Tizard, the mission visited the United States and Canada in the summer of 1940 to make available virtually all of Britain's technical and scientific military secrets. Overwhelmed by British generosity, the U.S. reciprocated. David Zimmerman tells the story of that mission and examines the importance of technology in modern war and its crucial role in the defeat of the Axis powers.

Zimmerman traces the early development of the mission from Britain's initial attempts at technical cooperation in World War I and unsuccessful efforts to restart it in the late 1930s. He highlights Winston Churchill's prominent, yet remarkably inconsistent, role in the story and the often tumultuous diplomatic relations with the Roosevelt administration. Among the secrets Britain revealed was the cavity magnetron, which made microwave radar possible.

The Tizard Mission established an effective system of teamwork for Allied technical and scientific cooperation, and it was this teamwork that proved to be a crucial factor in Allied technical superiority. It was also the beginning of the much longer story of Anglo-American scientific and technical cooperation. The Tizard Mission served as a model for the international technical cooperation that continues today in organizations such as NATO.