In 1850, he co-led the Bloody Island massacre of 60-200 Pomo old men, women, and children as part of the wider California genocide.

In 1866, he received brevet grade appointments as a major general of volunteers and in the regular U.S. Army for his Civil War service.

[1] On May 15, 1850, Davidson and Captain Nathaniel Lyon led a regiment of the 1st U.S. Dragoons in a massacre of the Pomo population of the island of Bo-No-Po-Ti in northern California.

[2] Following the Mexican-American War, Davidson was promoted to 1st Lieutenant and assigned to the Western frontier, where he served as the regimental quartermaster and adjutant.

During the Seven Days Battles he received brevet promotions in the Regular Army for his service at Gaines' Mill and Golding's Farm.

From August 10 to November 3, 1863, Davidson commanded the 1st Division of Frederick Steele's Army of Arkansas in his most distinguished role in the west.

Beginning November 27, 1864, Davidson was ordered to lead a 4,000 strong cavalry raid from the Union Army held Baton Rouge, to sever the M & O Railroad near State Line, Mississippi.

The raid was intended to divert resources away from Confederate John Bell Hood's operations near Nashville, and to threaten and harass Mobile.

Additionally, the raid was to support Sherman's March to the Sea by requiring the Confederates to keep resources in the Mobile theater of operations.

[7][8] On December 3, 1864, Davidson's Raiders crossed the Pearl River and entered Marion County, Mississippi, occupying Columbia the next day.

[9] On December 10, 1864, elements of Davidson's forces met two regiments of Confederate Cavalry near Leakesville, Mississippi at McLeod's Mill.

Finally, Lieutenant Albert Westinghouse, in command of the first squadron, was ordered to draw sabre and make a charge, which took them past the mill.

[12] Following the end of the Civil War, Davidson was again posted on the Western frontier, this time as a lieutenant colonel of the 10th Cavalry, known as the Buffalo Soldiers.