As to Sherman being repulsed, I assume you mean at Chickasaw Bluffs. I believe the correspondence shows that he would have never made the assault if he had been in contact with Grant. It may have been Grant that wrote that the lack of communications resulting from Van Dorn and Forrest is what helped throw the whole campaign into chaos. Washburn was stopped at Oakland, Dickey was stopped at Coffeeville, and Grant was stopped in Oxford by virtue of the Holly Springs raid. They had too many things going on and were too spread out. The river route consolidated the forces, and by a series of events Grant prevented any further intervention by McClernand, which also consolidated the command and re-defined the strategy and tactics of the objective, and ultimately put Grant firmly in control.