The ground occupied by the Confederate army, with one flank resting on the Potomac, and the other on the Antietam, which flowed in front, was advantageous. The creek was crossed by four stone bridges and a ford, and all except the northernmost bridge were strongly guarded. The land was occupied by meadows, cornfields, and patches of forest, and was much broken by outcropping ledges. McClellan only reconnoitred the position on the 15th. On the 16th he developed his plan of attack, which was simply to throw his right wing across the Antietam by the upper and unguarded bridge, assail the Confederate left, and when this had sufficiently engaged the enemy's attention and drawn his strength to that flank, to force the bridges and cross with his left and centre. Indeed, this was obviously almost the only practicable plan. All day long an artillery duel was kept up, in which, as General Hill says, the Confederate batteries proved no match for their opponents. It was late in the afternoon when Hooker's corps crossed by the upper bridge, advanced through the woods, and struck the left flank, which was held by two brigades of Hood's men. Scarcely more than a skirmish ensued, when darkness came on, and the lines rested for the night where they were. If Lee could have been in any doubt before, he was now told plainly what was to be the form of the contest, and he had all night to make his dispositions for it. The only change he thought it necessary to make was to put Jackson's fresh troops in the position on his left. Before morning McClellan sent Mansfield's corps across the Antietam to join Hooker, and had Sumner's in readiness to follow at an early hour. Meanwhile, all but two thousand of Lee's forces had come up. So the 17th of September dawned in that peaceful little corner of the world with everything in readiness for a great struggle in which there could be no surprises, and which was to be scarcely anything more than wounds for wounds and death for death. [Illustration: MAJOR-GENERAL HOWELL COBB, C. S. A.] [Illustration: MAJOR-GENERAL JOHN G. WALKER, C. S. A.] [Illustration: MAJOR-GENERAL LAFAYETTE McLAWS, C. S. A.]