Answer:
Trench warfare in World War I was employed primarily on the Western Front, an area of northern France and Belgium that saw combat between German troops and Allied forces from France, Great Britain and, later, the United States. Although trenches were hardly new to combat: Prior to the advent of firearms and artillery, they were used as defenses against attack, such as moats surrounding castles. But they became a fundamental part of strategy with the influx of modern weapons of war.
Long, narrow trenches dug into the ground at the front, usually by the infantry soldiers who would occupy them for weeks at a time, were designed to protect World War I troops from machine-gun fire and artillery attack from the air. As the “Great War” also saw the wide use of chemical warfare and poison gas, the trenches were thought to offer some degree of protection against exposure. (While significant exposure to militarized chemicals such as mustard gas would result in almost certain death, many of the gases used in World War I were still relatively weak.)
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