"That is what is so funny about war. The generals on both sides think they can win. But the only one who wins in a war is—me."
Monsieur Death was a personification of Death or the Grim Reaper.
In September 1916, a soldier in the trenches of Verdun began praying with his rosary before going into battle. Another soldier told him that it would do no good, since Monsieur Death would take whom he wanted. The prayer soldier was killed in the charge, and his body, still clutching the rosary, fell into the trench near Indiana Jones.
Later, returning from a successful intelligence gathering mission across no man's land, Jones was disoriented by a mortar shell. The specter of Death appeared before him as a grinning winged skeleton to inform Jones that it was time to join him on the journey after life. Jones resisted and the two argued over the futility of his actions and the war. Before Monsieur Death could take take him by force, Jones was approached by his superior, Gaston, who helped him to safety.