The famous military leader defeated at the Battle of Gettysburg was General Robert E. Lee. He commanded the Confederate Army during this pivotal Civil War battle in July 1863. Lee's strategy aimed to deliver a decisive blow to the Union forces, but his failure to secure victory marked a turning point in the war. The defeat weakened the Confederate position and bolstered Union morale. Gettysburg is often regarded as a significant moment in American history, illustrating the shifting tides of the conflict.