Banks and McDowell had the same belief.
McClellan was also at a loss.

Two or three scouts had brought in reports that it was marching toward Richmond, but he could not believe them.
The Secretary of War at Washington telegraphed to McClellan that the Union armies under McDowell, Banks, Fremont and Shields were to be consolidated in one great army under McDowell which would crush Jackson utterly in the valley.

At the very moment McClellan was reading this telegram the army of Jackson, far to the south of McDowell, was driving in the pickets on his own flank.
Jackson's men had come into a region quite different from the valley.
There they marched and fought over firm ground, and crossed rivers with hard rocky banks.

Now they were in a land of many deep rivers that flowed in a slow yellow flood with vast swamps between.

Most of it was heavy with forest and bushes, and the heat was great.