His purpose was one; to get his army across to the Vicksburg side and thence to prosecute his attack. First he tried a canal across the neck of the river peninsula opposite Vicksburg. Through this, if he could get the water to accept it as a new bed, he could take his forces below the city, out of reach of its guns, and cross over. But a flood burst into the unfinished canal and drowned out the plan. Then he tried to clear out a longer water route to do the same thing, through a string of bayous and rivers back in the Louisiana swamps. A fall in the river broke up this plan, as a rise had done that before it. Then he tried a longer route of the same sort, beginning at Lake Providence, seventy-five miles north of Vicksburg, but it was found impracticable. Then resorting to the east side of the Mississippi, he sent a naval expedition to try to penetrate Yazoo Pass, and thence through the inconceivable tangle of the Yazoo swamps and their rivers, to get behind the outer rebel defences north of Vicksburg, and so make a lodgment. But this plan was checkmated by the hasty erection in the heart of the swamp region, at the junction of the Tallahatchie and Yazoo Rivers, of a powerful fort, which the fleet tried in vain to silence. Then he sent another fleet to try another part of the same monstrous tangle, by way of the Big Sunflower River, but that effort miscarried much as the preceding one did. The obstinate commander had now tried six assaults upon his prey, and had been busily working at his failures for nearly four months. March 29th, 1863, he set his forces in motion for the seventh and successful effort. This was by what he had in fact recognized from the beginning as the best line of operation--by the south. It was however also the most difficult. As one of the historians of the war observes, a measure of the difficulties offered is given by the fact that General W. T. Sherman was not disposed to advise it. The same writer adds, "It can only be said that there was that in the composition of General Grant's mind that prompted him to undertake that which no one else would have adventured."