With the late discovery of Union forces crossing the Rappahannock and Rapidan Rivers in force—around 128,000 troops—Lee rapidly dispatches Stonewall Jackson and his corps to the West. Jackson leads three divisions on a long march around the Union right flank on 1 May, his units in position to strike late in the evening of the 2nd. Meanwhile, Lee took personal command of Lafayette McLaws and Anderson’s Divisions as they sought to hold back on-again-off-again attacks by the Union II, III, V, and XII Corps toward Fredericksburg. Jackson’s violent assault upon MG Howard’s IX Corps completed disrupted Hooker’s plan and he pulled his men into a tight perimeter, allowing Lee to consolidate his forces and focus them against the disordered Union lines. MG Sedgewick’s attack through Fredericksburg in the afternoon of 3 May was too little too late, and Lee handily redeployed his forces to crush the isolated Union force near Salem Church in the closing act of the Battle of Chancellorsville.