Most Secret War is R.V. Jones's account of his part in British Scientific Intelligence between 1939 and 1949. It was his responsibility to anticipate German applications of science to warfare, so that their new weapons could be countered before they were used. Much of his work had to do with radio navigation, as in the Battle of the Beams, with radar, as in the Allied Bomber Offensive and in the preparations for D-Day and in the war at sea.

He was also in charge of intelligence against the V-1 (flying bomb) and the V-2 (rocket) retaliations weapons and, although the Germans were some distance away from success, against their nuclear weapons.