How a Hotchkiss works.

The Hotchkiss M1909 machine gun was a light machine gun of the early 20th century, developed and built by Hotchkiss et Cie. It was also known as the Hotchkiss Mark I, Hotchkiss Portative and M1909 Benét–Mercié. It was based on a design by a Viennese nobleman and Austrian Army officer, Adolf Odkolek von Újezd, who sold the manufacturing rights to Hotchkiss in 1893. Several improved versions were designed by Hotchkiss's American manager, Laurence Benét and his French assistant, Henri Mercié.
As the Hotchkiss M1909 (or Mle 1909), firing the 8 mm Lebel, it was adopted by the French military in 1909 but not issued as an infantry weapon. The 700 examples manufactured were used in the fortresses at Verdun in a defensive capacity, on some fighter aircraft, and in Mark V* tanks acquired from Great Britain.

A variant to use the .303 round was produced in Britain at the Coventry factory as the "Hotchkiss Mark I". It was issued to some cavalry regiments, and the MkI* variant, with the wooden stock replaced with a pistol grip, was widely used in British tanks during World War I.

It was adopted by the United States in 1909 as the "Benét–Mercié Machine Rifle, Caliber .30 U. S. Model of 1909" firing the .30-06 cartridge. It was also used by other countries, including Belgium, Spain, Brazil and Australia. France and Britain used the Hotchkiss M1909 through World War I and on into World War II. The Australian Light Horse, the New Zealand Mounted Rifles Brigade, the Imperial Camel Corps, and the Duke of Lancaster's Own Yeomanry[4] used the Hotchkiss in the Sinai and Palestine Campaign (1915–17).U.S. forces used the Benét–Mercié at the Battle of Columbus in 1916 (4 guns fired 20,000 rounds total in the engagement), in the subsequent Pancho Villa Expedition in Mexico of 1916–17, and initially in France. Firing pins and extractors broke frequently on the American guns.

Some members of the U.S. press derisively called the M1909 the "daylight gun" because of the difficulty in replacing broken parts at night and jams caused when loading strips were accidentally inserted upside down in darkness. However, Major Julian Hatcher was assigned to look into the issue after Columbus and found almost all the issues were due to inadequate training. U.S. troops during the Villa Expedition received additional training and the M1909 was considered an effective weapon. It could have seen extensive use with the U.S. in World War I but production had already ceased and only a small number were available. The U.S. Navy still used them, however in that period.