While the canal work was in progress, McPherson’s Corps was assigned the opening of the Lake Providence route. The objective of this activity was the turning of Vicksburg’s left flank by passing southward through the Louisiana waterways to reach the bluffs below the city. A canal was cut to provide entrance from the Mississippi into Lake Providence, 75 miles above Vicksburg. From Lake Providence a route was surveyed through the labyrinth of bayous, lakes, and rivers by which a fleet might emerge again on the Mississippi 200 miles below the city and move on Vicksburg from the south. While presenting great difficulties to navigation, the entire 400 miles would be safe from enemy action. By the end of March 1863, McPherson’s men had almost cleared the route for navigation. The dredging of shoals and the sawing off of trees far enough below the water to permit passage of the transports proved the most severe obstacles. Before this long and extremely difficult route could be completed, however, other, more likely, plans were formulated, and the Lake Providence expedition was recalled. [Illustration: THE BAYOU EXPEDITIONS _FEBRUARY-APRIL 1863_] Four unsuccessful attempts by Grant to strike Vicksburg from the rear by moving his army on transports through the rivers and bayous to the bluffs north or south of the city. Yazoo Pass Expedition blocked by the guns of Fort Pemberton. Lake Providence Route abandoned; unable to clear route for navigation. Steele’s Bayou Expedition cut off in Rolling Fork. Duckport Canal Expedition abandoned because of low water in the bayous. THE YAZOO PASS EXPEDITION. The Yazoo Pass project, which sought to turn the right flank of Vicksburg by sending an expedition through the Delta waterways to the bluffs north of the city, was for a time the most promising of the bayou attempts. By exploding a mine in the Yazoo Pass, 325 river miles north of Vicksburg, access from the Mississippi into the rivers of the Delta was secured. With paddle wheels reversed against the roaring current which surged through the crevasse, and suffering extensive damage in collisions with trees and floating debris, the gunboats and transports carrying a division of infantry began the hazardous journey. Almost a month was required to reach the calmer waters of the Coldwater River.