the time Britain declared war on Germany, "our entire army had been in its operational positions for ten minutes." He also had his Chief of the General Staff increase the upper service eligibility age from 48 to 60 years (men of these ages would form the rear-echelon Landsturm units), and ordered the formation of an entirely new army corps of 100,000 men. Germany started planning the invasion of Switzerland on 25 June 1940, the day that France surrendered. At this point, the German army in France consisted of three groups with two million soldiers in 102 divisions. Recognizing that Switzerland and Liechtenstein were surrounded by Occupied France and the Axis Powers, Guisan issued Operationsbefehl Nr. 10, a complete overhaul of existing Swiss defensive plans. In this plan, the Fortress Saint-Maurice, the Gotthard Pass in the south, and the Fortress Sargans in the northeast would serve as the defence line. The Alps would be their fortress. The Swiss 2nd, 3rd, and 4th Army Corps were to stage delaying actions at the border, while all who were able were to retreat to the Alpine refuge known as the Réduit national. The population centres were, however, all located in the flat plains in the north of the country. They would have to be abandoned to the German forces in order for the rest of the country to survive. After the armistice with France, Hitler demanded to see plans for the invasion of Switzerland. Franz Halder, the head of the Oberkommando des Heeres (OKH), recalled: "I was constantly hearing of outbursts of Hitler's fury against Switzerland, which, given his mentality, might have led at any minute to military activities for the army." Captain Otto-Wilhelm Kurt von Menges in OKH submitted a draft plan for the invasion. Generaloberst Wilhelm Ritter von Leeb's Heeresgruppe 'C (HGr. C), led by Generalleutnant Wilhelm List and the 12th Army would conduct the attack. Leeb himself personally reconnoitered the terrain, studying the most promising invasion routes and paths of least resistance. Menges noted in his plan that Swiss resistance was unlikely and that a nonviolent Anschluss was the most likely result. With "the current political situation in Switzerland," he wrote, "it might accede to ultimatum demands in a peaceful manner, so that after a warlike border crossing a rapid transition to a peaceful invasion must be assured." The German plan continued to undergo revision until October, when the 12th Army