Through Clay's and Andrew Jackson's influence, President James K. Polk appointed Field as an "at large" cadet to the United States Military Academy.

In 1855, he was promoted to first lieutenant and assigned to the newly organized 2nd U.S. Cavalry, a regiment under Col. Albert Sidney Johnston that also included Robert E. Lee and numerous other future Civil War generals.

With the outbreak of the Civil War, Field resigned his commission on May 30, 1861, and left West Point for Richmond, where he offered his services to the Confederacy.

In May 1863, using crutches to move, Field was able to resume limited military duties, serving as Chief of the Bureau of Conscription in the War Department until July.

In the confused fighting in the Wilderness, Field suffered two minor wounds, but stayed in action throughout the Overland Campaign, including the Battle of Spotsylvania Court House.

When Lt. Gen. James Longstreet was wounded during a friendly-fire incident in the Wilderness, Field briefly assumed command of the First Corps, but he was later replaced by Maj. Gen. Richard H. Anderson, who had more seniority and combat experience.

He traveled abroad in 1875 and served Isma'il Pasha, the khedive of Egypt, as a colonel of engineers, helping train native officers and supervising several construction projects.

However, former fellow Confederate general Eppa Hunton argued that Field's service was under a private contract and that he had never sworn an oath of allegiance to the khedive.

[3] In the 20th century, the commonwealth of Kentucky erected a roadside marker on U.S. Route 62 near Versailles commemorating Woodford County's Civil War generals, including Field.