Joseph Hooker was an American Civil War general for the Union, chiefly remembered for his decisive defeat by Confederate General Robert E. Lee at the Battle of Chancellorsville in 1863.
Hooker had served in the Seminole Wars and the Mexican–American War, receiving three brevet promotions, before resigning from the Army. At the start of the Civil War, he joined the Union side as a brigadier general, distinguishing himself at Williamsburg, Antietam and Fredericksburg, after which he was given command of the Army of the Potomac.
His ambitious plan for Chancellorsville was thwarted by Lee's bold move in dividing his army and routing a Union corps, as well as by mistakes on the part of Hooker's subordinate generals and his own loss of nerve. The defeat handed Lee the initiative, which allowed him to travel north to Gettysburg.
Hooker was kept in command, but when General Halleck and Lincoln declined his request for reinforcements, he resigned. George G. Meade was appointed to command the Army of the Potomac three days before Gettysburg.