The movement of General Patterson's army against Harper's Ferry had been too obviously a feint to deceive either Davis or Lee, his chief military adviser. Johnston was given ten thousand men and able assistants including General Jackson.
On the tenth of July Beauregard, anxiously awaiting information of the Federal advance, received an important message from an accomplished Southern woman, Mrs. Rose O'Neal Greenhow. She had remained in Washington as Miss Van Lew had in Richmond, to lay her life on the altar of her country. During the administration of Buchanan she had been a leader of Washington society. She was now a widow, noted for her wealth, beauty, wit and forceful personality. Her home was the meeting place of the most brilliant men and women of the old régime. Buchanan was her personal friend, as was William H. Seward. Her niece, a granddaughter of Dolly Madison, was the wife of the Little Giant of the West, Stephen A. Douglas.
Before leaving Washington to become the Adjutant General of Beauregard's army Colonel Thomas Jordan had given her the cipher code of the South and arranged to make her house the Northern headquarters of the Southern secret service.
Her first messenger was a girl carefully disguised as a farmer's daughter returning from the sale of her vegetables in the Washington market. She passed the lines without challenge and delivered her message into Beauregard's hands.
With quick decision Beauregard called his aide and dispatched the news to the President at Richmond:
"I have positive information direct from Washington that the enemy will move in force across the Potomac on Manassas via Fairfax Court House and Centreville. I urge the immediate concentration of all available forces on my lines."
The Southern commander began his preparations to receive the attack.
The house on Church Hill had not been idle. Richmond swarmed with Federal spies under the skillful guidance of Socola.
General Scott knew in Washington within twenty-four hours that Beauregard was planting his men behind the Bull Run River in a position of great strength and that the formation of the ground was such with Bull Run on his front that his dislodgment would be a tremendous task.