The Johnson light machine gun is one of the lesser-known US military machine guns of WWII, although it seems to have been very popular with all those who used it in combat. Melvin Johnson made a commendable attempt to get his rifles adopted by the US military, but was unable to unseat the M1 Garand as American service rifle. However, he did make a significant sale of both rifles and light machine guns to the Dutch colonial army.
By the time those Dutch guns were ready to ship, however, the Japanese had overrun most of the Dutch islands. The guns were thus basically sitting on the docks with nowhere to go, and at that point the US Marine Corps took possession of them. Because of their short recoil action and quickly removable barrels, the Johnson guns were ideal for airborne Paramarines, and saw use in the Pacific with these forces. They were also used by the joint US/Canadian First Special Service Force in Italy.
In many ways, the Johnson LMG is similar to the German FG-42, although with more emphasis on full-auto use instead of shoulder rifle use. It fired from a closed bolt in semiauto and from an open bolt in full auto, and had a bipod both effective, light, and easily detachable. Overall the Johnson is a light, handy, and very easily dismantled weapon, and its popularity with combat troops seems well deserved.