During the Punitive Expedition in Mexico, some US soldiers were also equipped with M97s. Already popular before World War I, sales of the Model 1897 picked up after the war broke. This was because many were produced to meet the demands of the military. When the United States entered World War I, there was a need for more service weapons to be issued to the troops. It became clear to the United States just how brutal trench warfare was, and how great the need was for a large amount of close-range firepower while fighting in a trench, after they had observed the war for the first three years. The Model 1897 Trench grade was an evolution of this idea. The pre-existing Winchester Model 1897 was modified by adding a perforated steel heat shield over the barrel which kept the soldier's hands off a hot barrel, and an adapter with bayonet lug for affixing an M1917 bayonet.