Question

why was the d - day invasion crucial for the allies europe first strategy?
the invasion forced germany to surrender.
the invasion ended german ambitions to invade the united states.
the invasion was key in forcing the germans to retreat east.
the invasion exhausted german supplies and weakened their defenses.

Explanation:

The D - Day invasion on June 6, 1944, established a Western front in Europe. This forced the Germans to fight on two major fronts (the existing Eastern front against the Soviet Union and the new Western front), which led to their retreat eastwards. Germany did not surrender immediately after D - Day. Germany had no real plans to invade the US mainland during World War II. While supply issues were a factor in Germany's weakening over time, the key impact of D - Day was the creation of a new front and the push eastwards.

Answer:

The invasion was key in forcing the Germans to retreat east.