Before the outbreak of World War II, Grousset had published his two most important works, Histoire des Croisades (1934-1936) and L'Empire des Steppes (1939).
Setelah pecahnya Perang Dunia II, Grousset menerbitkan dua karya paling berpengaruhnya, Histoire des Croisades (1934-1936) dan L'Empire des Steppes (1939).