My contribution I think fits the bill, although my spin on it may not be popular.
In the summer of 1941, Germany invaded the Soviet Union in a surprise attack that never should have been a surpise given the amount of intelligence coming out of Germany into Soviet hands. The Germans quickly pushed past the borders of the recently-absorbed Baltic republics and surrounded Leningrad by the beginning of September. Over the next 900 days (or so), the siege continued as the German were unwilling to expend the men and materiels necessary to take the city and the Soviets were unable to dislodge the Germans. Resupply became possible only during the winter months via the ice roads of Lake Lagoda. Best estimates put the civilian casualties at about 1.1M, mostly from starvation and/or exposure, although many were killed in the continual shelling that the city endured over the 3-year siege. Enough shrapnel remains in the trees surrounding the Peterhoff palace that it is dangerous to be in the gardens during a thunderstorm because of the increased lightening strikes. There are still signs in place on the Nevski Prospekt (a major street) directing pedestrians to cross to the other side of the street during shelling. For more, see
http://en.wikipedia.org/wiki/Siege_of_Leningrad
Obviously the Soviet Union bore the brunt of the German assault and suffered more casualties than any other country or group, including European Jews (not to diminish their suffering, but they were a numerically smaller group to begin with). Red Army estimates for WWII are about 18.5M, which is probably low considering the Soviet's penchant for arresting and executing their own. Civilian casualties are an additional 12M, which again is probably low. Personally, I give the majority of the honors for defeating the Nazis and Germans to the Soviets and the Red Army since they bore the brunt of the fighting and had turned the tide well before D-Day in 1944. The citizens of Leningrad are a great example of those who sacrificed to beat the German war machine.