Final answer:
The Western Front was considered a stalemate until the entry of the US troops with their industrial capacity and manpower shifted the balance leading to an Allied victory.
Step-by-step explanation:
The Western Front was considered a stalemate until the US "doughboys" arrived in 1917-18. Trench warfare made the front a deadly deadlock where neither the Allies nor the Central Powers could secure a decisive victory. The trenches stretched from the English Channel to the Swiss Alps, signifying a constant standoff that resulted in enormous casualties without significant territorial gains.
However, the entry of the United States into World War I brought fresh troops and massive industrial support, which tipped the balance in favor of the Allies. With the German supply lines and resources stretched thin after years of intensive war, the American forces, under the command of General Pershing, played a crucial role in halting the German advances and eventually turning the tide towards an Allied victory.
Advances in military technology had caused the stalemate, rendering traditional battlefield strategies ineffective. The introduction of machine guns, artillery, and other modern weapons made offensive maneuvers extraordinarily costly. The arrival of the US troops, combined with their resources, provided the necessary impetus for an Allied offensive that ultimately led to the end of the war.