Western Allies Forces: The Western Allies, primarily the United States, Britain and France, were Germany's main opponents on the Western Front. The Allies had a number of advantages over Germany, including a larger population and industrial base, more natural resources, and a greater ability to produce and transport war material. The Western Allies also had the advantage of being able to fight on interior lines, which allowed them to move troops and supplies more quickly and easily than Germany.
Eastern Front: The vast, open steppes of Eastern Europe favored mobile warfare and the Red Army was able to use its superior numbers to overwhelm the Germans in a series of massive battles.
Oil: Germany did not have adequate domestic sources of oil and relied heavily on imports from Romania and the Soviet Union. The Allies were able to cut off these supplies, severely hampering Germany's ability to wage war.
Logistics: Germany was not as well-equipped as the Allies in terms of logistics, such as transportation and supply chains. This made it difficult for them to move troops and supplies to the front lines, and it also hindered their ability to respond to sudden changes in the situation.
Manpower: Germany faced a critical manpower shortage, especially in the later stages of the war. The constant fighting had depleted their reserves and they were unable to replace their losses.
Strategic Bombing: The Allied strategic bombing campaign was devastating to Germany's infrastructure and industrial base. The bombing raids destroyed factories, transportation hubs, and communication systems, making it difficult for Germany to produce war material and transport troops and supplies.