Why were the forces of World War I engaged in stalemate until 1917?

The stalemate on the Western Front of World War I occurred for a number of reasons. First, the Germans wanted to focus on defeating Russia in the East, and they chose a stalemate in the West. The stalemate was part of the larger military strategy of Germany. The weapons available for defense (artillery, repeating rifle, machine guns) favored this strategy. In addition, the strategy of the French and British for attacking this defensive strategy was outdated and did not account for the new technologies. The destructive nature of the new weapons also had an impact on the battlefield which hampered an offensive strategy. Artillery shells damaged no man's land between the trenches to the point that it was difficult to launch an offensive with heavy weapons.  Even movement of troops was also difficult. Communication lines were also ruptured by artillery and gunfire which caused communication breakdowns that made it difficult to launch offensives at effective times. The tank and the introduction of fresh American troops to the front helped to put an end to the stalemate.