Albert Sidney Johnston , (born February 2, 1803, Washington, Kentucky, U.S.—died April 6, 1862, Shiloh, Tennessee), commander of the Confederate forces in the Western theatre during the early stages of the American Civil War (1861–65). His battlefield death was considered an irreparable loss by the South. He was the highest-ranking soldier on either side to die in battle during the war.

Johnston grew up in the small but thriving frontier town of Washington, Kentucky. His father, who enjoyed a successful practice as one of the area’s few physicians, had relocated his family there from New England. After studying at private schools, Johnston matriculated at age 15 in nearby Lexington at Transylvania University, which operated one of the foremost medical schools in the country before the Civil War. There he was a conscientious student. In 1821–22 Johnston altered his career path from medicine to the military and gained appointment to the United States Military Academy at West Point, where he befriended future Confederate president Jefferson Davis. Once again he excelled in his studies, graduating eighth in a class of 41 cadets in 1826.

Johnston married Henrietta Preston in 1829. After serving as a staff officer in the Black Hawk War (1832), he left the army in 1834 to care for his wife, who was dying of tuberculosis. In 1836, following the outbreak of the Texas war for independence, Johnston enlisted as a private in the Texan army. He quickly rose through the ranks and was named the army’s commander with the rank of brigadier general (though he was prevented from actually taking command as a result of injuries sustained in a duel). In 1838 Johnston became the secretary of war for the fledgling Republic of Texas, and during the Mexican-American War (1846–48) he commanded Texas volunteers. Johnston considered Texas his home for the rest of his life.

After Texas became part of the United States, Johnston returned to the U.S. Army and in 1855 was appointed commanding officer of the 2nd U.S. Cavalry Regiment.