He defended cavalry as an independent branch of service and opposed conversion of mounted troops into mechanized or armored units.

Herr's affection to horse, "somewhat quixotic" for the period, temporarily made him "a hero and a standard bearer" to generations of officers indoctrinated in cavalry tactics.

[1] German blitzkrieg in Poland and France compelled the military leadership in favor of armoured warfare, and the United States cavalry was mechanized contrary to Herr's objections.

In 1911 he was summoned back to West Point as an instructor, promoted to First Lieutenant and then assigned to the 11th Cavalry Regiment based in Fort Oglethorpe, Georgia.

He turned down the offer to join the United States Tank Corps and instead became Chief of Staff of the 30th "Old Hickory" Division, a National Guard formation under the command of Major General Edward Mann Lewis.

By his energy and zeal, and persistent efforts, coupled with sound tactical judgment, Colonel Herr contributed to the success of the operations.

Cavalrymen expected promotion of Bruce Palmer (senior) but instead Chief of Staff Malin Craig selected Herr.

After the outbreak of World War II Herr followed the European campaigns through attaché reports that reinforced his belief in superiority of cavalry tactics.

His chief of staff Willis D. Crittenberger pre-screened these reports and jotted "cavalry mission" in the margins to attract Herr's attention.

[17] The proposal, delivered at the War College in September 1939, was bundled with the demand that new armored units should be formed from scratch rather than converted from horse troops.

According to Bruce Palmer Jr., the request forced officers of all grades to "cut their throats professionally": they had to bet their careers on obsolete war technology, or risk immediate repercussions from their Chief.

After the Louisiana maneuvers of May 1940 the participating officers drafted the "Alexandria recommendations" calling for the establishment of an independent Armored Force.

The Armored Force was created July 10, 1940, with Chaffee in command,[21][22] but as late as November 1940 Herr and Chief of Infantry George A. Lynch opposed creation of a separate combat arm.

[28] Herr retired to his home in Washington, D.C., which stood just one mile away from the White House, and remained informed of the military politics through correspondence with fellow officers.

He blamed his fall on the alleged conspiracy of General Staff officers seeking promotions in the newly formed Armored Forces.

[29] The stalemate of the Korean War, wrote Herr, could be avoided had the U.S. military employed "... really mobile cavalry, mounted on horses and trained to fight on foot.

"[8] In 1953 Herr and historian Edward S. Wallace co-authored The story of the U.S. Cavalry, 1775-1942, a book intended "to light up, a little, the past glory and glamour of the men on horseback" rather than provide a comprehensive history of the service.