During WWI, John Browning designed the M1918, Browning Automatic Rifle for the U.S. Army as a replacement for the French-made Chauchat that U.S. forces had previously been issued. It was designed to be carried by infantrymen, supported by a shoulder sling with the butt fitted into a cup on the Mills belt so it could be fired from the hip. The concept of “walking fire” never actually worked in any practical sense. The BAR was a difficult weapon to use because of its open bolt operation and strong recoil spring – additional range practice and training was required in order for the soldier to master the rifle without flinching. However, the BAR was effective in its role as a portable, shoulder-fired automatic rifle.