After studying in England, he was appointed a midshipman on January 1, 1812, and attended the Naval academy at Washington, D.C., until 1 August when he was assigned to the frigate Constellation.

When his ship tried to slip out to sea, the strong British squadron operating in the Chesapeake Bay forced her to put into Norfolk, Virginia.

Tattnall's battery and a force of American boats gave the attackers a sound rebuff that deterred the British from further attempts to take the city.

Tattnall was promoted to commander on February 25, 1836, and, in April, reported for a three-year tour of duty at the Boston Navy Yard.

During the Mexican–American War, he took part in the attacks on Vera Cruz, San Juan d'Ulloa, and Tuxpan, and he suffered an arm wound.

At Hong Kong on January 29, 1858, he relieved Commodore James Armstrong taking command of the East India Squadron, breaking his flag in San Jacinto.

During his two years in the Far East, Commodore Tattnall violated American neutrality while commanding the chartered steamer Toey-Wan, when he came to the assistance of a British and French squadron under fire from the Taku Forts at the mouth of the Pei Ho or Hai River.

[2] On his return voyage early in 1860, Tattnall commanded the Powhatan, carrying the first diplomatic embassy from Tokugawa Japan to the United States.

While stopped at Honolulu, Hawaii along the way, the British residents of that city wrote a letter thanking Tattnall for his "gallant and humane conduct" during the "unfortunate affair at the Pei-ho River".

[3] The embassy was safely conveyed to San Francisco and then Panama, where they crossed the isthmus and continued on to Washington, D.C. At the outbreak of the Civil War, Capt.

Tattnall commanded Southern naval units during the defense of Port Royal until the harbor was captured by Union forces on 7 November 1861.

On May 11, 1862, in the face of advancing Federal forces, Flag Officer Tattnall ordered the destruction of his flagship, CSS Virginia (ex-Merrimack).