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At
Centreville, on Saturday night,
McDowell called his officers together and announced to them his plan of battle for the following day. The
Warrenton turnpike ran almost directly west from
Centreville to
Gainesville station on the railroad.
He was yet unaware that
Johnston had joined
Beauregard, and sought to prevent such junction by seizing
Gainesville.
Beauregard's army lay in detachments behind
Bull Run, at five different fords, along a line of eight miles. His left and northernmost flank was at the stone bridge where Warrenton turnpike crosses
Bull Run, though Mc-Dowell supposed it to extend to the first ford above.
The bridge was a solid stone structure of two arches, of considerable size and height, connecting the precipitous and rocky eastern bank of the stream with a broad piece of level bottomland on the west.
The bridge was thought to be defended in force, and said to be prepared for blowing up. The engineers had information, however, that Sudley Ford, two or three miles above, could be readily carried and crossed by an attacking column.
McDowell therefore ordered that
Tyler, with the heaviest division, should advance from
Centreville directly to
Stone Bridge, three and a half miles distant, and make a feigned attack; while
Hunter and
Heintzelman should make a secret and circuitous night march northward,
