The enemy just before them allowed no idle moments.
Yet Grant, as happened later on at Shiloh, was taken by surprise.

When the first roar of the battle broke with the dawn he was away conferring with the wounded naval commander, Foote.

His right, under McClernand, had been caught napping, and eight thousand Southern troops striking it with a tremendous impact just as the men snatched up their arms, drove it back in heavy loss and confusion.

Its disaster was increased when a Southern general, Baldwin, led a strong column down a deep ravine near the river and suddenly hurled it upon the wavering Union flank.
Whole regiments retreated now, and guns were lost.

The Southern officers, their faces glowing, shouted to each other that the battle was won.