Manassas is in the north central area of Virginia. Not far from Washington, DC. And Johnston's army was hardly encamped there waiting on the Federals to attack. Jackson's "men of the valley" force marched (and rode the rails) to that site to reinforce PGT Beauregard AND Johnston. Who had also travelled to the area at the possibility of armed conflict. You should read up on whatever you are copying and pasting from. Please. "Mannassa Plains" was the name of a large Jewish farm in northern Virginia and hense became known as Manassas in later references. Virginia heritage and history runs DEEP.
Keith