Final answer:
Trenches were built on the Western Front in World War I due to the stalemate and defensive strategies employed by both sides. They provided protection for soldiers and created a line of defense that was difficult to break through.
Step-by-step explanation:
The trenches were built on the Western Front during World War I as a result of the stalemate and the defensive strategies employed by both sides. The new technologies of war, such as machine guns and modern rifles, made charging and trying to take the enemy's position ineffective and costly. The trenches provided protection for soldiers and allowed them to defend their position against enemy attacks.
The Race to the Sea, where both sides tried to maneuver their forces north to outflank the other, resulted in the construction of a network of trenches that stretched from the English Channel to the Swiss Alps. The trenches provided a line of defense that was difficult for either side to break through, resulting in years of stalemate and the trapping of soldiers in the trenches.
As the war progressed, the trenches became more elaborate and developed, with the Germans digging deeper and creating a complex system. The trenches formed a frontline where soldiers would rotate positions and where artillery and machine-gun nests were located. Behind the frontline trenches were secondary trenches, artillery positions, and field hospitals.