What decision by Confederate General Robert E Lee do to alter the plans of the Union to attack Lee's army in December of 1863?

Answer 1

In late 1863, Lee now safe in Virginia, for the time being, was able to refresh his army from the ill fated raid into Pennsylvania. He positioned the Army of Northern Virginia in a strong defensive posture. On the other hand, General Meade, head of the Army of the Potomac wanted to advance against Lee, unless Lee had created a favorable position for his army which he did. Nevertheless, Meade believed by advancing he would abort the number of drafted Southern recruits into Lee's forces. At the same time Meade was concerned that the Army of the Potomac would not be able to take advantage of the Union's draft law to reinforce his own army. Also, the fortifications constructed by Lee, although not overwhelming, detered Meade as well.

Here then was a rift between Lincoln and his general in chief , Henry W. Halleck. Halleck believed that an advance was necessary, while Lincoln was more cautious and advised Meade to "act threatening" but not to advance. Lincoln had come to the conclusion that a stalemate in Virginia was acceptable. It is another case of the President, with good intentions, not following the advice of his general in chief. It was these types of interference that hampered the Union's war efforts.

Answer 2

Fortification played a large role in the US Civil War. Lee's decision to fortify Mine Run altered General Meade's attempt to attack the Army of Northern Virginia in early December, 1863.