Dent was born on December 17, 1820, in White Haven, St. Louis County, Missouri.

[1] Dent was assigned as brevet second lieutenant to the 6th US Infantry, served in the Southern campaign during the Mexican–American War, and was brevetted first lieutenant and captain for gallant and meritorious conduct at Contreras, Churubusco and at Molino del Rey respectively.

[2] He served for 16 years on frontier duty, taking part in the Yakima War, and in March 1863 was promoted to major in the 4th US Infantry and was stationed in New York to suppress anticipated riots.

[2] On April 5, 1865, President Abraham Lincoln appointed Dent brigadier general of volunteers to rank from April 5, 1865, but the President did not submit the nomination to the U.S. Senate before his death ten days later, so Dent's appointment was not immediately confirmed.

[3] Eventually, President Andrew Johnson submitted the nomination on January 13, 1866, and the U.S. Senate confirmed it on February 23, 1866.