Then he divined the plan.

Jackson was making this circuit through the woods to fall on the Northern flank.
It was the first of the great turning movements which Lee and Jackson were to carry through to brilliant success so often.
"Look at the red blaze beyond those bushes," said Dalton, "and listen how rapidly the sound of the battle is growing in volume.

I don't know where we are, but I do know now that Old Jack is leading us right into the thick of it." The general rode forward and stopped his horse on the crest of a low hill.

Then Harry and Dalton, looking over the bushes and swamps, saw a great blue army stationed behind a creek and some low works.
"It's McClellan!" exclaimed Dalton.
"Or a part of him," said Harry.
It was a wing of the Northern army.

McClellan himself was not there, but many brave generals were, Porter, Slocum and the others.