With the outbreak of the American Civil War in 1861, Ward rejoined the army, and became the colonel of the 38th New York Infantry Regiment.

By early 1864, he had developed a strong reputation as a military leader, although there had been an incident when he panicked and fled the field during a night attack at Chancellorsville.

After his removal from military service, Ward served as a clerk in the New York court system, and was struck and killed by a train while vacationing in 1903.

After receiving an education from Trinity Collegiate School, he enlisted as a private in the 7th United States Infantry Regiment in August 1842, at the age of 18.

[3] After the outbreak of the American Civil War, Ward used his military experience and political connections to gain a commission as colonel in the 38th New York Infantry Regiment.

Part of Orlando B. Willcox's brigade, the 38th New York deployed behind two Union artillery batteries on Henry House Hill.

At that battle, Ward had briefly led the brigade his regiment was in, after Brigadier General David B. Birney was temporarily removed from command.

[4] At the Battle of Fredericksburg, Ward's brigade was engaged against the portion of the Confederate line defended by Stonewall Jackson's men.

[16] While his panicked flight at Chancellorsville was an embarrassment for him, Ward's military career suffered no long-term harm from the incident.

Another staff officer claimed to have later encountered Ward on the caisson and to have suggested he dismount and attempt to rally his men.

[24] Four days later, in the Battle of Spotsylvania Court House, Ward's men participated in an attack against Confederate lines in the Laurel Hill area.

[25] May 12, in another phase of the fighting at Spotsylvania Court House, saw Ward's brigade participate in an attack that broke a major hole in the Confederate line.

[21] Charles Dana, the Assistant Secretary of War, had written a letter dated May 9 stating that Ward had been arrested for "running away in the Wilderness battle".

[28] Ward was never brought to trial; historian Harry W. Pfanz suggests that this was due to his multiple wounds and long military career.

[29] He received an honorable discharge on July 18, and the United States Secretary of War refused requests to restore Ward to the service and then hold a trial to ascertain if he was guilty of the charges or not.