[1] Dispatched to France with the American Expeditionary Force during World War I, Keiser was quickly promoted to temporary captain and appointed to command of 1st Battalion, 6th Infantry Regiment, a unit of the 5th Division.

After his assignment at West Point, Keiser returned to Fort Sam Houston as the commander of a company in the 9th Infantry.

In January 1944, he was promoted to brigadier general and assigned as chief of staff of the Fourth Army at Fort Sam Houston.

[citation needed] He returned to China in 1948, this time as part of the United States Military Advisory Group to the Nationalist Chinese Government.

In February 1950, his former West Point classmate Joe Collins gave him command of the division, together with a promotion to major general.

The 25th Division was able to withdraw to Anju, but Keiser was unable to obtain permission from Major General John B. Coulter to follow.

[7] Following the Battle of the Ch'ongch'on River, during which 2nd Division suffered crippling losses of approximately 4,000 men,[7] Keiser met with Major General Leven Cooper Allen, the chief of staff of the Eighth Army, in Seoul.

He was relieved of his command and replaced with Major General Robert B. McClure, supposedly for medical reasons, although he felt he was being made a scapegoat for the reverses suffered by the United Nations following the Chinese intervention in the war.