During this last action, Campbell was wounded by an exploding artillery shell and was sent back to the United States to recover from severe shrapnel injuries to his back. During his recuperation, he made appearances at numerous war bond rallies. Campbell hoped to return to combat and was reassigned to his squadron in November 1918. By then however the war was winding down and he saw no further frontline action before the Armistice of November 11, 1918. While leaving active service the following year, he continued to hold a commission in the reserves until 1924.