Staff Writer (Updated: 9/26/2016):
The Model 1893 was inevitably improved through the upcoming "Model 1897" which featured a reinforced receiver (to handle the new smokeless powder shells, a rarity for shotguns of the time) and lengthened shoulder stock. Otherwise, the conventional pump-action slide arrangement remained the same and the receiver still retained the true Winchester-style appearance. At the onset of World War 1 (1914-1918), Winchester had evolved their already-popular Model 1893 line into the "Model 1897". This invariably produced a specially designed variant recognized as the "Trench Gun" to suit a US military requirement for a close-range weapon of exceptional reliability and considerable stopping power. The Model 1897 fit the bill and changes to the design included a shorter 20-inch barrel, a perforated heat shield fitted over the barrel and a special bayonet adapter devised by the specialists at the Springfield Armory. Overall, the weapon remained the same trusted-and-true 12-guage long gun fitting five shells within a tubular magazine under the barrel assembly. The weapon held a unique facility in which the trigger could remain pressed and the gun fired in rapid succession through actuation of the pump slide allowing a well-trained operator to loose all five rounds quickly. In confined placed such as trenched and buildings, this proved an advantage. 1,024,700 Model 1897s were produced and utilized by all US military branches during the war. The weapon, amazingly, went on to see continued service throughout World War 2, the Korean War and the Vietnam War despite its 1890s origination.
In 1912, Winchester engineer Thomas Crosley Johnson took to refining the Browning-inspired Model 1897 series further to produce the "Model 1912" of 20-gauge form. The hammer was now entirely housed within the frame to provide a smoother, cleaner appearance - a standard since adopted by all shotgun manufacturers. The wooden stock was well-formed to incorporate the pistol grip aft of the traditional trigger group. The barrel was tapered with the tubular magazine underslung in the usual way. A ribbed slide was set over this installation and operated in a conventional fashion. Shells were loaded through a port under the receiver and each manually-actuated pump of the slide would introduce a new shell into the chamber while ejecting any spent shells out of a right-side port on the receiver. Construction was primarily of steel with metal components machined and furniture of wood. Certainly a very refined weapon, it was a further evolution of the line of Winchester shotguns originating from 1893. The Model 1912 retained the quick-firing trigger-pump "function" of the Model 1897 before it. In 1914, a 12- and 16-guage Model 1912 became available with the 12-guage form managing six shells from the tubular magazine.
For the United States military in World War 1, the Model 1912 appeared in a fully-militarized form mimicking the changes as forced upon the Model 1897 Trench Gun (shorter barrel, heat shield and provision for a bayonet). Form and function were largely unchanged from the civilian version of the shotgun, the action remaining manual through operation of the slide and trigger. The US Army alone procured 20,000 of the type (designated as the "Model 12" or "M12") when going to war in Europe in 1917. As "trench guns" they served their purpose, supplying exceptional hitting power within short ranges resulting in German protests of the use of such weapons by war's end - ironic considering the use of poison gas by the Germans against the Allies in the same war. Trench guns were named after the trench warfare emerging during the early years of World War 1, bogging down a once fluid, mobile fronts into warzones of bloody attrition and stalemate. World War 1 ended with the German surrender in November of 1918, the original Model 12 Trench Guns being produced into the early 1920s.