Staff Writer (Updated: 12/1/2016):
The French Army of World War 1 had grown to appreciate the concept of automatic weapons at the infantry level and, when the Americans committed to the war in 1917, the French passed on this appreciation to its newly arriving ally. "Walking Fire" was the term given to the concept of a standard infantryman wielding a weapon firing volumes of ammunition at the enemy. As trench warfare permeated the battlefields across Europe at this time, weapons of voluminous fire was required to clear obstacles like stubborn, dug-in enemies.
Browning went to work to develop such a weapon and settled on a gas-operated system which relied in a piston moving within a cylinder assembly. The assembly was fitted under the barrel and the open-bolt action contained in a rectangular, nearly featureless receiver. A "hump" along the top of the receiver was forced by the upwards cammed bolt lock. The extraction port was set to the right side of the receiver in the usual way. The magazine feed was found just ahead of the trigger unit and the shoulder support of the weapon constituted a traditional rifle-style butt. Wooden furniture made of this component as well as the handguard under the forward mass of the weapon. Magazines were straight in their general design and angled along their bottoms. A forward and rear iron sight allowed for some accurized fire at range.
The M1918 showcased some deficiencies in its design - it relied on a complex internal mechanism for operation and its machining process meant that it was expensive to built and time consuming as well. However, this also led to a weapon that was utterly reliable in the worse of battlefield conditions and virtually indestructible as military firearms go.
The weapon was designed, developed and trialed in short order. Initial models were fielded with a firing selector which allowed the operator to choose form single (semi-automatic) or full-automatic fire to be achieved. In time, this feature was dropped in favor of a rate-of-fire selector which the operator could set between 350 or 550 rounds-per-minute.