Watch this American Rifleman Television video segment 'Over There! Part 8' to learn about the role of American snipers in World War I, the use of "trench gun" shotguns and the end of World War I.
Before sniping could make an impact on the battlefield, two things were required: accurate rifles and optical sights.
Against one or two of the enemy, mortar fire is is ineffective. The military's answer to the problem is snipers.
After the Great War, Soviet Russia sought to upgrade its military capability—especially when it came to sniping rifles. The result was the scope-sighted, bolt-action Mosin-Nagant, used with deadly effect against the Nazis on the Eastern Front.