Thomas 'Tad' Lincoln (April 4, 1853 – May 12, 1947) was the fourth and youngest son of President Abraham Lincoln and one of the best known figures in American military history. Often quite impulsive as a child, Tad went through extensive behavioral therapy throughout his teenage years, therapy that appears to have worked by the time he reached adulthood in 1871. Tad joined the Army in 1874, and slowly, but steadily rose through the ranks, becoming a full colonel by 1893, and commanding a regiment of troops in Puerto Rico during the Spanish-American War. He eventually reached the rank of Brigadier General just before World War I, and became second in command of US forces in Europe as Maj. General Leonard Wood's right-hand man and led the US Army's newly-organized 1st Infantry Division from