What, then, was the plan of battle of which the first step was this movement of Hooker's? McClellan's dispositions on the 15th were made whilst Franklin's corps was still absent, and, under the orders he received, was likely to be so for a day at least. [Footnote: Official Records, vol. xix. pt. i. p. 29.] Sumner's two corps had been treated as the centre of the army in hand, Burnside's had been divided by putting Hooker on the extreme right and the Ninth Corps on the extreme left, and Porter's corps was in reserve. This looked as if a general attack in front with this organization of the army were intended. But the more McClellan examined the enemy's position the less inclined he was to attack the centre. He could cross the bridge there and on the right, and deploy; but the gentle slopes rising toward Sharpsburg were swept by formidable batteries and offered no cover to advancing troops. The enemy's infantry was behind stone fences and in sunken roads, whilst ours must advance over the open. Lee's right rested upon the wooded bluffs above the Burnside bridge, where it could only be approached by a small head of column charging along the narrow roadway under a concentrated fire of cannon and small arms. No point of attack on the whole field was so unpromising as this. Then, as Jackson was still at Harper's Ferry, there was the contingency of an attack in rear if anything less than the mass of our army were pushed beyond Lee's right. On our right, in front of Hooker, it was easy to turn the Confederate line. The road from Keedysville through Smoketown to the Hagerstown turnpike crossed the Antietam in a hollow, out of the line of fire, and a march around Lee's left flank could be made almost wholly under cover. The topography of the field therefore suggested a flank attack from our right, if the National commander rejected the better strategy of interposing his army between Lee and Jackson as too daring a movement. This flank attack McClellan determined to make, and some time after noon of the 16th issued his orders accordingly. In his preliminary report of the battle, made before he was relieved from command, McClellan says:-- "The design was to make the main attack upon the enemy's left,--at least to create a diversion in favor of the main attack, with the hope of something more, by assailing the enemy's right,--and as soon as one or both of the flank movements were fully successful, to attack their centre with any reserve I might then have in hand." [Footnote: O R., vol. xix. pt. i. p. 30.] His report covering his whole career in the war, dated August 4, 1863 (and published February, 1864, after warm controversies had arisen, and he had become a political character), modifies the above statement in some important particulars. It says:--