The railway bridge across it had been wrecked by the retreating Confederates and he was compelled to wait there two weeks until his engineers could reconstruct it.
War plays singular chances.

Halleck in St.Louis, secure in his plan of campaign, had sent an order after Dick left Shiloh, for Buell to turn to the north, leaving Grant to himself, and occupy a town that he named.
Through some chance the order never reached Buell.

Had it done so the whole course of American history might have been changed.

Grant himself, after the departure of the earlier messengers, changed his mind and sent messengers to Nelson, who led Buell's vanguard, telling him not to hurry.

This army was to come to Pittsburg Landing or Shiloh partly by the Tennessee, and Grant stated that the vessels for him would not be ready until some days later.