Between April and June of 1940, Germany invaded Norway, Denmark, the Netherlands, Belgium, and Luxembourg consolidating power across neutral Western Europe. On June 22, 1940, France signed an armistice with Germany, which divided France between the German-occupied territory in the north and the Vichy regime in the south. Although officially neutral, the French state during this time was generally pro-Nazi and cooperated with Germany’s racial policies.
Germany's last offensive on its Western front, Operation Wacht am Rhein, was an offensive launched towards the vital port of Antwerp in December 1944. Launched in poor weather against a thinly-held Allied sector, it achieved surprise and initial success as Allied air power was stymied by cloud cover. However, stubborn pockets of defence in key locations throughout the Ardennes, the lack of serviceable roads, and poor German logisitics planning caused delays. Allied forces deployed to the flanks of the German penetration, and Allied aircraft were again able to attack motorized columns. However, the stubborn defense of US units and German weakness led to a defeat for the Germans.
Inmates at Birkenau numbered around 100,000 at their peak. They were of many different nationalities, but the vast majority of those that entered the camp were unregistered Jews, many of whom were immediately sent to their deaths in the gas chambers. Women and children stood the least chance of survival, and many died even before arriving at Birkenau due to the appalling conditions of the railway journeys. The unloading platform, where the brisk selection process was conducted, remains. Apart from physically fit men (who often perished later from the rigours of the camp) it was often only an accident of birth that merited a possibility of survival. Large numbers of twins survived until liberation as they were objects of interest to the research of Dr. Josef Mengele - a man disliked even by his Nazi peers.
SS-Obergruppenführer Reinhard Heydrich, head of the Reich Main Security Office (Reichssicherheitshauptamt or RSHA), convened what became known as the Wannsee Conference on 20 January 1942 at Am Großen Wannsee 56–58, a villa in Berlin's Wannsee suburb. The meeting had been scheduled for 9 December 1941, and invitations had been sent on 29 November, but it had been postponed.
Hitler had spent four years in World War One fighting a static war with neither side moving far for months on end. He was enthralled by Guderian’s plan that was based purely on speed and movement. When Guderian told Hitler that he could reach the French coast in weeks if an attack on France was ordered, fellow officers openly laughed at him. The German High Command told Hitler that his “boast” was impossible. General Busch said to Guderian, “Well, I don’t think that you’ll cross the River Meuse in the first place.” The River Meuse was considered France’s first major line of defence and it was thought of as being impossible to cross in a battle situation.