Was the Battle of Shiloh intentional or accidental?

Answer 1

Intentional.

Two Confederate units had managed to unite at Corinth, and were in a hurry to attack Grant's army before General Buell could bring support to him from the East.

Grant was not expecting this attack and was caught off-guard. On the first day, his army was almost pushed into the Tennessee River, but it rallied just in time, as Buell was arriving.

Only one Brigade had been kept on alert throughout and that was commanded by John McClernand, who claimed that he was responsible for the victory. This caused serious feuding between Grant and McClernand for the rest of the campaign.