Answer:
It enabled Southern troops to mount an offensive to invade the North.
Step-by-step explanation:
The battle of Chancellorsville was a monumental victory for General Lee's Confederate Army. His tactics had defeated a larger Unionist Army. It came at a great human cost, and a personal loss for the Confederate leadership: the death of General Stonewall.
However, defeat demoralized the Union and embolden Lee to launch an offensive. His idea was that he had to show strength to convince Brittan and France to aid the Confederation as the clear winning side.