How did lee with 45000 men able to defeat hooker who had 70000 men at Chancellorsville?

Answer 1

Because of the mistakes committed by Hooker. They were:

1 - He ordered to the VI and I Corps successful landed at Fredericksburg after crossing the River Rapahannock on April 29, 1862, to form a strong bridgehead limiting themselves to defend it. Therefore they remained idles on the place.

2 - In the evening of the same day he sent the whole Stonemans's Cavalry Corps, out of 1,250 men, to carry a raid behind the Confederate lines, thus depriving his army of the indispensable support of scouting and covering.

3 -On May 1st, after brilliatly managing to seize the pivotal position of Chancellorsville, with 54,000 men, after a while increased upto 75,000, Hooker claimed " to wait for Lee's attack to come". Instead to carry hastily on the outflanking movement towards Fredericksburg, he advanced in a very slowly and hesitant way as he were being caught by "the fog of war". Evidently the fatal effects of the absence of his cavalry began to be felt.

Lee took advantage of those mistakes and decided to split his army into two part.

He left 10,000 men at Fredericksburg to guard and keep at bay the inactives Union Corps standing there.

He sent four divisions (McLaws of I Corps, A.P. Hill, Rodes and Colton of II Corps and Stuart's Cavalry Corp., to join the division Anderson (for a total of about 52,000 men) and form a defensive line at Tabernacle's Church to face and check Hooker's 75,000.

When his divisions clashed against the Confederate entrenchments, finding a sturdy resistance, Hooker, ignoring how strong the opponent were and lest of being outflanked, ordered to withdraw back to Chancellorsville, where the army had to stand on the defensive.

At that point, Lee received intelligence from his cavalry, that informed that the extreme Union wing near Wilderness Church was divided from the Rapidan by an undefended gap of about 5 kilometers and therefore susceptible to be outflanked and attacked from the rear.

He then, on May 2nd, decided to further split his army in front of the enemy and ordered his II Corps and Fitzhugh's cavalry division (30,000 men) under Stonewall Jackson to put in motion the relevant displacement and carry out the assault.

The terrible impact of the 30,000 confederates against the end of the enemy line broke into piece the Union IX Corps, whose units fled disorderly. It seemed that the entire Federal right wing was about to collapse. But Hooker and his competent Corps Commanders were able to restore a new defensive line about one and half kilometer before Chancellorsville, avoiding the encirclement of their entire army.

The battle was not over yet, but after that awful blow, its trend was clearly turning in favor of the Confederates.

On May 3rd, pressed by Lee's attacking forces, Hooker took the fatal decision to evacuate the pivotal position of Hazel Grove, thus allowing the link between the two Confederate wings and forcing the Federals to retreat from Chancellorsville and set up a new line in form of an acute angle, whose ends were leaning on the Rivers Rapidan and Rappahannock.

The contemporary seizing of the Confederate positions at Fredericksburg by the Union Corps was of no avail to change the outcome of the battle.

In the afternoon of May 4th they were half encircled by three Confederate divisions and forced to hastily crossing over the Rapahannock to avoid their annihilation.

On May 5th Hooker retreated his army, recrossing the Rapahannock at United States Ford.