Project MX-981, Effects of Deceleration Forces of High Magnitude on Man, was initiated in 1945 by the U.S. Army Air Force Aero Medical Laboratory at Wright Field, Ohio to confirm the feasibility of a "40 g" crash restraint system for pilots of military aircraft. Captain John Paul Stapp, MD, was selected to carry out this work. This paper provides historical background and perspective for that project, and summarizes Dr. Stapp's work on that Project at Edwards AFB, California, and his subsequent tests at Holloman AFB, New Mexico.