A 1911 graduate of the Virginia Military Institute (VMI), Gerow served with the United States occupation of Veracruz and on the Signal Corps staff on the Western Front during World War I.

[4] Prior to World War I, Gerow served in a series of assignments as a company grade officer in the Infantry.

[5] He was promoted to the temporary rank of lieutenant colonel, in charge of purchasing all the radio equipment for the American Expeditionary Forces (AEF) in Belgium and France.

[2] The citation for his Army DSM reads: The President of the United States of America, authorized by Act of Congress, July 9, 1918, takes pleasure in presenting the Army Distinguished Service Medal to Lieutenant Colonel (Signal Corps) Leonard Townsend Gerow, United States Army, for exceptionally meritorious and distinguished services to the Government of the United States, in a duty of great responsibility during World War I. as Officer in Charge of the Sales and Disbursing Division of the Signal Corps.

On 1 September 1940, prior to the American entry into World War II, he became a colonel in the permanent grade and a month later, on 1 October 1940, he became a temporary brigadier general.

[2] On handing over the position of the Chief of War Plans Division to Dwight Eisenhower, Gerow told him: "Well, I got Pearl Harbor on the book; lost the PI [Philippine Islands], Sumatra and all the NEI [Netherlands East Indies] north of the barrier.

"[10] In October 1942, Gerow became Commanding General (CG) of the 29th Infantry Division, an Army National Guard formation recruiting largely from Virginia and Maryland,[2] although the Chief of Staff of the United States Army, General George C. Marshall, had doubts about Gerow's ability.

[13][14][15] He was awarded an oak leaf cluster to his Distinguished Service Medal on 8 August 1944, for his contributions to the planning phase of Operation Overlord.

While fighting was still raging in and around Paris, Major General Gerow, displaying marked valor, courageously drove through intense 20 mm machine gun and sniper fire to reach the city.

Although many intersections were blocked with barricades manned by German troops, he proceeded unhesitatingly through the dangerous streets to effect an important conference with the Commanding General of the French forces within the city.

Major General Gerow's gallant action was an inspiration to the members of his command and reflects great credit upon himself and the military service.

[12] In the gap between the two periods of command he returned to the United States to appear before the Army Board's Pearl Harbor Investigation.

The resulting Clausen Report found fault with Gerow's performance, citing his failure to keep Lieutenant General Walter Short fully informed and to give him clear guidance.

[16] Eisenhower and Bradley held Gerow in high regard and ranked him as one of the top American field commanders of World War II.

In a February 1945 memo General Eisenhower listed the principal American commanders in order of merit based on the value of their service during the war.

[3] Gerow died at Kenner Army Hospital at Fort Lee, Virginia, on 12 October 1972, and was buried in Arlington National Cemetery.