Grant’s landing was unopposed, partly because of two diversionary movements and partly because of Pemberton’s decision to hold his army close to Vicksburg and fight a defensive campaign. Both diversions were completely successful. On April 17, the day after Porter’s running of the batteries had indicated Grant’s strategy of striking from the south, Col. B. H. Grierson with 1,000 cavalrymen moved out from southwestern Tennessee on one of the celebrated cavalry raids of the war. They rode entirely through the State of Mississippi behind Pemberton’s army to a junction with Union forces at Baton Rouge, La. In 16 days Grierson covered 600 miles, interfering with Confederate telegraph and railroad communications and forcing Pemberton to detach a division of infantry to protect his supply and communication lines. Sherman, whose corps had not yet made the march from Milliken’s Bend, made an elaborate feint above Vicksburg. Loading his men aboard every available gunboat, transport, and tug, he landed at Haynes’ Bluff, north of Vicksburg, leading Pemberton to expect the real attack from that direction. Both moves helped screen Grant’s true objective. The events immediately following Grant’s landing revealed a basic difference in tactical concepts between Pemberton, commanding the Army of Vicksburg, and Gen. Joseph E. Johnston, his superior, who was in charge of Confederate operations in the West. Johnston believed that to defeat Grant it would be necessary for Pemberton to unite his whole force in order to smash the Union Army, preferably before Grant could consolidate his position on the east bank. Accordingly, he wired Pemberton on May 2 “If Grant’s army crosses, unite all your troops to beat him; success will give you back what was abandoned to win it.” It was Pemberton’s concept that holding Vicksburg was vital to the Confederacy and that he must primarily protect the city and its approaches. To have marched his army to meet Grant “would have stripped Vicksburg and its essential flank defenses of their garrisons, and the city itself might have fallen an easy prey into the eager hands of the enemy.” This inability of Pemberton and Johnston to reach agreement upon the tactics that might thwart Grant’s invasion seriously affected subsequent Confederate operations and prevented effective cooperation between the two commanders in the Vicksburg campaign. [Illustration: _Maj. Gen. William Tecumseh Sherman, commanding the Union XV Corps._ Courtesy National Archives.] [Illustration: _Gen. Joseph E. Johnston, commanding Confederate military operations in the West._ Courtesy National Archives.] THE BATTLE OF PORT GIBSON.