Of the curving line of the union army, the left was the corps of General Burnside, the centre the corps of General Porter, and the right the corps of General Hooker; but in the rear of Hooker was the corps of General Mansfield, and behind it that of General Sumner, while the force of General Franklin, just up from Pleasant Valley, acted as the reserve.
McClellan’s plan of the battle was to make the principal attack from his right, but as soon as that was well engaged, to throw Burnside from his left against the right of Lee, not absolutely as a real attack, but by menacing the road to the ford which was Lee’s only line of retreat, to occupy and divert certain portions of the Confederate army, and thus reduce its power of resistance to the real attack upon the other flank.
By reason of the curvation of the line, our batteries in its centre could reach effectively the whole extent of the front of the enemy from left to right; and throughout the day, as opportunity offered, the guns did good execution, and more especially upon our right where we could annoy the rebel infantry while in the cover of the woods, and enfilade them whenever they appeared in the open glade.
At break of day the rattling volleys of musketry on the right told that Hooker was opening the great struggle. Soon occasional deep thuds of his cannon were also heard, then nearer and more constant came the sounds approaching from both wings, until our own batteries in the centre joined in the din. Along the whole line gun for gun came back--as if echoed from the other ridge--the voice of the invading army from lips of bronze and iron, and its exploding messengers repeated in our ears the arguments of war, until hundreds of heavy guns were united in one deep quivering roar. And although there was rising and falling in the sound, yet until nightfall the sound of battle never ceased.
Just across the creek the skirmishers of our corps showed like dotted lines upon the fields; now and then we could see the smoke puff from their rifles, although the sound was lost in that of the general conflict. On the left, until afternoon, no movements were visible, but across that open glade, far away on the right, the tide of battle ebbed and flowed.