He also headed a War Department investigation into the role that military intelligence played before the Japanese attack on Pearl Harbor.

In his work for the Military Intelligence Division, he was instrumental in 1943 in starting the Venona project.

Late in his career, he also worked as an assistant to Allen W. Dulles, who was Director of Central Intelligence.

[2] In a 1959 interview, Clarke said that he disagreed with the decision to drop atomic bombings on Japan at the end of World War II and believed it had been unnecessary since Japan was "down to an abject surrender through the accelerated sinking of their merchant marine and hunger alone, and when we didn't need to do it, and we knew we didn't need to do it, and they knew we knew we didn't need to do it, we used them as an experiment for two atomic bombs.

Carter Clarke Jr. is a retired United States Army brigadier general who in 1996 founded Gemesis Corporation, the largest manufacturer of gem-quality synthetic diamonds.