He served in the French Army in World War I on the Western Front.
From 1927 to 1930 Blanchard was the deputy chief of staff for the French Army of the Rhine.
Blanchard took over the First French Army Group on 23 May 1940 following the accidental death of General Gaston Billotte.
The First Army Group ceased to exist on 29 May 1940, six days after Blanchard took command.
[2] Blanchard was awarded the Grand Cross of the Legion of Honour in early June 1940 by French premier Paul Reynaud at the recommendation of Maxime Weygand, in honor of his actions which allowed the escape of so many soldiers at Dunkirk.