Hood's education at the United States Military Academy led to a career as a junior officer in both the infantry and cavalry of the antebellum U.S. Army in California and Texas. At the start of the Civil War, he offered his services to his adopted state of Texas. He achieved his reputation for aggressive leadership as a brigade commander in the army of Robert E. Lee during the Seven Days Battles in 1862, after which he was promoted to division command. He led a division under James Longstreet in the campaigns of 1862–63. At the Battle of Gettysburg, he was severely wounded, rendering his left arm useless for the rest of his life. Transferred with many of Longstreet's troops to the Western Theater, Hood led a massive assault into a gap in the Union line at the Battle of Chickamauga, but was wounded again, requiring the amputation of his right leg.

Hood returned to field service during the Atlanta Campaign of 1864, and at the age of 33 was promoted to temporary full general and command of the Army of Tennessee at the outskirts of Atlanta, making him the youngest soldier on either side of the war to be given command of an army. There, he dissipated his army in a series of bold, calculated, but unfortunate assaults, and was forced to evacuate the besieged city. Leading his men through Alabama and into Tennessee, his army was severely damaged in a massive frontal assault at the Battle of Franklin and he was decisively defeated at the Battle of Nashville by his former West Point instructor, Maj. Gen. George H. Thomas, after which he was relieved of command.

After the war, Hood moved to Louisiana and worked as a cotton broker and in the insurance business. His business was ruined by a yellow fever epidemic in New Orleans during the winter of 1878–79 and he succumbed to the disease himself, dying just days after his wife and oldest child, leaving ten destitute orphans.

In 1862, an infirmed Sam Houston, who as governor opposed secession, freed Joshua and his entire slave staff.  Months later, a grateful Joshua Houston offered penniless Sam Houston’s widow Margaret Lea Houston $2,000 in gold, his life savings.  She refused the gesture, and encouraged him instead to use the money for his family.  Houston married three women in his lifetime and had eight children, including Atlanta University graduate and celebrated educator Samuel Walker Houston.  

Freedman Houston bought property, built a home, and opened a prosperous blacksmith shop.  Houston and other freedmen then in 1867 founded the Union Church, Huntsville, Texas’s first black institution.  He also led the effort to establish a small school for African American children in the same community.  Joshua Houston entered local politics, serving as an alderman in Huntsville and county commissioner in Walker County.  A lifelong advocate of education, he secured funding for the building in 1883 of another school, Bishop Ward Normal and Collegiate Institute. His son, Samuel Walker Houston, in turn, founded the first high school for black students. Joshua Houston died in 1902 in Huntsville, Texas.  He was 80.