For extraordinary heroism while attached to the 6th Regiment, U.S. Marines, in actual conflict with the enemy and under fire during the advance on Bouresche, France, on 6 June 1918. In the hottest of the fighting when the marines made their famous advance on Bouresche at the southern edge of Belleau Wood, Lt. (j.g.) Osborne threw himself zealously into the work of rescuing the wounded. Extremely courageous in the performance of this perilous task, he was killed while carrying a wounded officer to a place of safety.