Final answer:
Longstreet disagreed with Lee's plan at Gettysburg due to concerns about the Union's strong position and doubts about his own troops' ability to execute the plan. He advocated for a defensive strategy instead.
Step-by-step explanation:
Longstreet did not want to go through with Lee's plan at Gettysburg because he believed the Union position was too strong. He thought it would be better to move the Confederate Army around the Union flank and fight a defensive battle. Additionally, Longstreet did not believe his men could get into position in time to effectively carry out Lee's plan.
Learn more about Longstreet's disagreement with Lee's plan at Gettysburg