In 1862, Thomas Jackson had done it again. The Union army was beaten fairly and squarely. Robert E. Lee's strategy had once again been proven victorious by sending Jackson's "Foot Cavalry" on a wide outflanking march, around John Pope's Union Army of Virginia, and had, along with Longstreet's attack, annihilated it more or less entirely.
This thread continues from Action Jackson -1862: Stonewall's Foot Cavalry Wins The Day

The Union Strikes Back by David AtwellEven the Union Capital, Washington DC, came under threat from Lee's Confederate Army of Northern Virginia, not to mention its actual occupation after a five hour long battle.

It was in this light, then, that all Union forces, especially those of George McClellan's Army of the Potomac, reacted in trying to retake the Union capital from Rebel control. Nothing was certain and fear gripped the Union as to what was Lee's next move. More to the point, deep down no Union general, nor soldier for that matter, thought that they could defeat Lee. And as a result the American Civil War could soon come to an end in favour of the Rebs.A Chapter from Hancock 1862

Lincoln, though, having regained his composure, after fleeing Washington in rather indigent fashion, immediately sacked McClellan, as commanding general of the Army of the Potomac, and replaced him with Ambrose Burnside who was, at the time, consider a highly capable general and possibly just the man who could push Lee out of Washington and all the way back to Richmond. Given the fact that the Army of Northern Virginia was much weakened, by its assault upon the Union capital, this was seen as a distinct possibility.

Lee, meanwhile, was well aware of the dangers, especially in the light that his old warhorse, James Longstreet, had been wounded during the attack on Washington's defences. Thankfully Longstreet's wound was not life threatening, and he was able to convalesce in one of Washington's many fine dwellings, though he was never far from Lee if required. Having said that, the Army of Northern Virginia was down to around 35 000 able soldiers at the beginning of September 1962. This alone made Lee think that the capture of Washington was not worth the price of victory.
Read the whole story of Hancock 1862 - the Union Strikes Back on the Changing the Times web site.