This picture depicts a Heer soldier of the Wehrmacht on the Eastern Front of World War Two.
The Eastern Front was by far the most deadly Front of the Second World War. It produced the most casualties seen during the conflict, and included the deadliest battle in human history: the Battle of Stalingrad with around 2 million dead, captured, or missing.
The sheer size of each conflict in the east outshined any engagement to the west, in the Mediterranean region, the Far East, or the Pacific.
Just in 1941, during Operation Barbarossa, 6 million casualties were taken in total, and that was less than 6 months of fighting.
Over the next 3+ years, a brutal push and pull warfare would dominate the region, but after the Battles of Stalingrad and Kursk, the Red Army became dominant over the German Wehrmacht and Waffen SS.
The Germans began a tactical retreat, and they actually carried it out quite well considering their situation and the fact that the Soviets outnumbered them in men, tanks, and aircraft immensely.
But, a nicely fought retreat does not win wars, and Germany slowly got pushed back through the western USSR, then into Poland, and finally, the Fatherland and other close German held territories.
A last ditch effort was made to regain lost oil fields in Hungary in early 1945, known as Operation Spring Awakening, but this failed once the Red Army was able to suppress the German troops. Vienna, Austria, was taken by the Soviets as a result of the Red Army counter-attack during this operation.
The Germans lost because of the fact that they did not have the manpower, the armor, the aircraft, or the fuel to fight on so many fronts against so many world powers.