Framing History: Grant, Rawlins, and the Tale of the Missing Tail
Union Gen. John A. Rawlins served for much of the war as Gen. Ulysses S. Grant’s adjutant or chief of staff. Their strong professional partnership was matched by a close personal friendship that had taken root before the war in their hometown of Galena, Illinois.

Their kinship, at times, could provide an amusing reprieve from the pressing stresses of war bearing down on them. Such was the case when Rawlins’ prized horse met with a comical mishap. The bay horse had been a gift from Galena friends to commemorate Rawlins’ appointment to Grant’s staff in August 1861. Rawlins was known to be particularly fond of its lavishly long tail. One morning, Rawlins found the tail had been reduced to a two-inch stub. At the sight of it, the excitable Rawlins raged and declared that should he ever find the enemy who did it, he would shoot him.
An amused Grant, through fits of laughter, explained that the “enemy” was likely not human, but an army mule that had munched the tail off. “Well, general,” Rawlins replied with exasperation, “I hope that some night a mule will eat off the tail of your old yellow horse—and then see how you’ll like it.” For months, Grant remained amused by the horse’s shortened tail, spontaneously laughing at the sight of it when he found himself riding behind Rawlins.
This photograph at the Library of Congress shows an African American boy on John Rawlins’ horse, most likely at City Point in 1864. The tail looks suspiciously touched up or drawn on.

Source:
Ottens, Allen J. General John A. Rawlins: No Ordinary Man. Indiana University Press. 2021. 194-195
The tale (no pun intended) of a mule eating the tail of a horse is assured to elicit a smile, and even a chuckle in this readers case.
That is a great note about Rawlins, Melissa. He was the first major for the 45th Illinois Infantry, before Grant summoned him to be his chief of staff. Not quite 1/3 of the 45th Illinois came from Jo Daviess county, with many of the officers and some enlisted men knowing Grant before the war.