May 1865
After the surrender of Lt. Gen. Richard Taylor and his Confederate army in Alabama and Mississippi on Thursday, May 4, there remained only Confederate troops under Gen. Kirby Smith in the Trans-Mississippi; Brig. Gen. Jeff Thompson’s troops in Arkansas; and Brig. Gen. Stand Watie’s Indian Brigade in the Indian Territory (now Oklahoma).
On May 6, the Federal War Department issued orders setting up the military commission to try the alleged Lincoln assassination conspirators.