By the spring of 1918 it became evident that we would require a special machine gun for use in our tanks. Several makes of guns were considered for this purpose and finally discarded for one reason or another. The ultimate decision was to take 7,250 Marlin aircraft guns which were available and adapt them to tank service by the addition of sights, aluminum heat radiators, and handle grips and triggers. The rebuilding of these guns at the Marlin-Rockwell plant when the armistice was signed was progressing at a rate that insured the adequate equipment of the first American-built tanks. Meanwhile the Ordnance Department undertook the production of a Browning tank machine gun. This gun was developed by taking a heavy Browning water-cooled gun, eliminating the water jacket and substituting an air-cooled barrel of heavy construction, and adding hand grips and sights. The work was begun in September, 1918, and the completed model was delivered by the end of October. Before the armistice was signed five sample guns had been built, demonstrated at the Tank Corps training camps, and unanimously approved by the officers of the Tank Corps designated to test it. After a test in France, the report stated: "The gun is by far the best weapon for tank use that is now known, and the Department is to be congratulated upon its development." An order for 40,000 Browning tank guns was given to the Westinghouse Co. This concern, already equipped for the manufacture of heavy Browning guns, was scheduled to start its deliveries in December, 1918, and to turn out 7,000 tank guns per month after January 1, 1919. After the signing of the armistice, however, the order was cut down to approximately 1,800 guns. By March 27, 1919, the company had delivered 500 Browning tank guns, and the order for the remaining 1,300 was thereafter canceled. After the entrance of the United States in the war the armies on both sides developed a new type of machine-gun fighting, which consisted in indirect firing, or laying down barrages of machine-gun bullets. This required the development of special tripods, clinometers for laying angles of elevation, and other special equipment; and speedy progress was being made in the quantity production of this matériel when the war came to an end.