This week 150 years ago in the Civil War, Joseph Hooker was sacked as commander of the Union’s Army of the Potomac, replaced by George G. Meade.

Hooker had served only months in the leadership post, promoted there by President Abraham Lincoln in January 1863 in place of Maj. Gen. Ambrose Burnside after Burnside’s disastrous stint at the helm.

Hooker was felled by infighting despite his deft moves to reorganize the Union army and better supply it with arms and rations for the fighting still ahead. But his undoing began at the Battle of Chancellorsville, Va., in early May 1863 when Confederate Robert E. Lee outsmarted and divided a far larger Union force, seizing a key victory. Only days ahead, Meade would meet and defeat Lee at the historic Battle of Gettysburg in July 1863.

Already there were ominous signs that Lee’s invasion of the North was on track. The Associated Press reported in a dispatch June 21, 1863, that Confederate cavalry had captured a number of horses near Hagerstown, Md., and that some 6,000 Confederate troops were on the northern side of the Potomac River. A second AP dispatch reports “rebels, in heavy force, were advancing on Pittsburg(h), Pa.”

In fact, Lee had been moving forces forward for days, poised to redirect fighting away from war-ravaged Virginia to the north — moving within potential striking distance of several Northern cities that also included Philadelphia and Baltimore.