A portion of this line was covered by the Warwick Creek, which he dammed up to make it unfordable, and erected batteries to guard the dams. Across the intervening ground a weak earthwork with trenches was constructed, there being no time to raise stronger works; but Magruder relied chiefly upon the swampy and difficult nature of the country, and the concealment afforded by the forest, which rendered it difficult for the enemy to discover the weakness of the defenders.

He posted 6,000 men at Yorktown and Gloucester Point, and the remaining 5,000 troops under his command were scattered along the line of works to the Warwick River. He knew that if McClellan pushed forward with all his force he must be successful; but he knew also that if the enemy could but be held in check for a few days assistance would reach him from General Johnston's army.

Fortunately for the Confederates, the weather, which had been fine and clear during the previous week, changed on the very day that McClellan started. The rain came down in torrents, and the roads became almost impassable. The columns struggled on along the deep and muddy tracks all day, and bivouacked for the night in the forests. The next morning they resumed their march, and on reaching the first line of intrenchments formed by the Confederates found them deserted, and it was not until they approached the Warwick Creek that they encountered serious opposition. Had they pushed forward at once they would have unquestionably captured Richmond. But McClellan's fault was over-caution, and he believed himself opposed by a very much larger force than that under the command of Magruder; consequently, instead of making an attack at once he began regular siege operations against the works on Warwick Creek and those at Yorktown.