Valmy (välmēˈ) [key], village (1993 est. pop. 293), Marne dept., NE France, in the Argonne region. The "cannonade of Valmy," a Franco-Prussian artillery skirmish, was fought near there on Sept. 20, 1792. This was the first important engagement in the French Revolutionary Wars. Although heavy rain brought an inconclusive halt, the encounter revealed the superiority of French artillery.