While Marine Recon got its start in World War II, with the Raiders and the 1st Marine Division’s Amphibious Reconnaissance Company, much of what Recon is today is thanks to Marine Test Unit 1.
After the nuclear bombing of Hiroshima and Nagasaki, most of the US military started trying to shift their doctrine to a model of a nuclear battlefield. At the time, it was assumed that nuclear weapons would become an integral part of warfare, much like gas had in WWI. As a result of this shift in doctrine, the services started looking at how to operate in a nuclear environment.
In 1946, Col. Robert Cushman (later to become Commandant of the Marine Corps) authored a staff report to the Commandant, Gen. Vandegrift. In this report, Col. Cushman argued that the kind of mass amphibious landings of WWII were no longer viable on the nuclear battlefield–the massed amphibious formations moving into a relatively small beachhead would be easy targets for tactical nuclear weapons. He presented the idea that the Marine Corps had to broaden its focus to a dispersed area of operations up to 200 miles deep, spreading its units around so as to make smaller and harder to hit targets. In this way, a single nuke couldn’t take out the better part of a Marine Division.
At the time, Col. Cushman’s concepts for increased mobility and dispersion weren’t within the Marine Corps’ capabilities. It wasn’t until the helicopter operations in Korea in 1951 that it began to look like it was possible.