On October 14, 1918 during the Meuse–Argonne offensive, Adler accompanied by fellow officer supervised the work of clearing the enemy from Saint-Juvin in the Ardennes department in northern France. They suddenly came upon a party of the enemy numbering 150 Germans. Adler, armed only with his pistol, opened the fire on the enemy and ran toward the party, calling on them to surrender. His bravery and good marksmanship resulted in the capture of 50 Germans, and the remainder fled. For this act of valor, Adler was decorated with Distinguished Service Cross, the second highest decorations of the United States military for valor in combat.