He enlisted in the Navy in 1944, then was transferred to the Army the following year upon receiving an alternate appointment from South Dakota to the United States Military Academy at West Point.

In 1953, Warner was reassigned to Europe where he served as a company commander and battalion staff officer in Trieste, Italy, Austria, and West Germany.

After earning a Masters of Science in International Relations from George Washington University, in 1969 Warner assumed command of the 3rd Brigade, 4th Infantry Division in the Central Highlands of Vietnam.

On 25 April 1981, Secretary of Defense Caspar Weinberger announced that the RDJTF would become a separate command with responsibility for Southwest Asia.

Rebuffed in his attempt to renew the mandate of his command, Warner requested retirement, citing a lack of support from the Joint Chiefs of Staff during the debate.

On 18 August 2005, Warner's granddaughter, First Lieutenant Laura Margaret Walker, was killed in action in Delak, Afghanistan, making her the first female West Point graduate to die in combat.

Colonel Warner recommended that SAC Trimbach's request be refused, and also that the FBI change its standing orders from shoot–to–kill to shoot–to–wound, in light of the fact that the Indians were not trying to harm anyone.

The symbolic presence of the U.S. Army, in the person of Colonel Warner, is credited with blocking the all–out attack that the FBI and its allies had in mind.

[5] The first use of the phrase is identified as a quote in the Christian Science Monitor (11 April 1980) in reference to the Iran hostage crisis: "US options grow more difficults [sic] as the chance of a Soviet response increases.

However, many American strategists now argue that even light, token US land forces – 'getting US combat boots on the ground' as General Warner puts it – would signal to an enemy that the US is physically guarding the area and can only be dislodged at the risk of war.