 Over 13,000 men marched into Northern Virginia on the 24th, bringing with them "a long train of wagons filled with wheelbarrows, shovels, &c." These implements were put to work even as thousands of men marched further into Virginia.Engineer officers under the command of then-Colonel John G. Barnard accompanied the army and began building fortifications and entrenchments along the banks of the Potomac River in order to defend the bridges that crossed it.By sunrise on the morning of the 24th, ground had already been broken on the first two forts comprising the Civil War defenses of Washington — Fort Runyon and Fort Corcoran.