Wyndham, who had studied medicine in England, served as a surgeon in the Union Army during the American Civil War. He was present at the battles of Fredericksburg, Chancellorsville and Gettysburg and served with General Banks throughout the Red River Campaign. He resigned from the army in 1864 to join the Grove stock company that was then headed by John Wilkes Booth. After Booth assassinated Lincoln, Wyndham, considering himself a failure as an actor, went back to England. After a brief return to medicine he resumed his acting career and soon became a success.