Ranald Mackenzie, the eldest son of a naval commander, was born in New York City on 27th July, 1840. He graduated from West Point first in his class. He immediately joined the Union Army and during the American Civil War was wounded six times and won four brevets for gallantry. General Ulysses Grant described him as the "most promising young officer in the army". By the end of the war he was a Major General of Volunteers.

In 1870 Mackenzie became colonel of the 4th Cavalry and the following year became commander at Fort Concho in Texas. In 1871 he was badly wounded by a Comanche arrow. After he recovered he led an attack deep into Mexico in order to punish warriors from the Kickapoo.

In 1874 Comanche and Kiowa war parties began attacking settlers in Texas. At first these hit and run tactics were difficult for the army to deal with and be the time they arrived on the scene of the attack the war parties had disappeared. Over 3,000 troops were brought into Texas from neighbouring states to deal with this problem. Mackenzie eventually discovered the winter camp of the Native Americans who had been carrying out raids on the settlers. In September 1874 Mackenzie launched a dawn attack on the camp in Palo Duro Canyon and destroyed the village, stole their supplies and took away their horses. That winter, unable to survive by hunting, the warriors were forced to surrender to the authorities.

Mackenzie was placed in command of Fort Sill in 1876 but the following year moved to Fort Clark. He was criticized by some people for his harsh treatment of the Ute who were moved from Colorado to Utah in 1881. Later that year he took command of the District of New Mexico.

In 1883 returned to Sante Fe and took command of the Department of Texas. Mackenzie's behaviour became more erratic and he was treated for mental instability. In 1884 Brigadier-General Mackenzie was forced into retirement.

Ranald Mackenzie died on 19th January, 1889.