When World War II began, Blanchard took command of the First French Army near Cambrai, France, as part of General Gaston Billotte's 1st Army Group. When Germany invaded on 10 May 1940, Blanchard followed the prearranged French strategic plan, moving his army forward to the Dyle River in support of the Belgians. He had the British Expeditionary Force (BEF) under Lord John Gort on his north flank and General André Corap's Ninth French Army to the south. After advancing approximately 25 miles, Blanchard encountered General Walther von Reichenau's German Sixth Army and was forced to withdraw and join those Allied troops cut off by the German drive down the Somme River to the English Channel.
Following Billotte's death in an automobile accident on 25 May 1940, a shattered Blanchard took over command of the 1st Army Group. British colleagues, such as General Alan Brooke, grimly noted that he was "merely existing and hardly aware of what was going on around him," completely bewildered and incapable of issuing orders. On 29 May, a harassed Brooke even threatened to have Blanchard shot if his orders disrupted Brooke's evacuation plans. On 1 June 1940, Blanchard left Dunkerque for Britain on a French destroyer, and in late August, he was placed on the French army's reserve list. Thereafter, he faded into obscurity, although he was later awarded the Grand Cross of the Legion of Honor. Blanchard died at Neuilly-sur-Seine on 23 November 1954.
Alanbrooke, Lord. War Diaries, 1939–1945. Ed. Alex Danchev and Daniel Todman. London: Phoenix Press, 2001.; Crémieux-Brilhac, Jean-Louis. Les Français de l'an 40. 2 vols. Paris: Gallimard, 1990.; Draper, Theodore. The Six Weeks' War: France, May 10–June 25, 1940. New York: Viking, 1964.; Horne, Alistair. To Lose a Battle: France 1940. Boston: Little, Brown, 1969.; Spears, Edward L. Assignment to Catastrophe. 2 vols. New York: Wynn, 1954–1955.