Final answer:
The Battle of Gettysburg marked a turning point in the war and ended the threat of Confederate invasion.
Step-by-step explanation:
The battle that marked a turning point in the war and prevented the Confederacy from threatening the US with invasion was the Battle of Gettysburg. This battle took place from July 1 to July 3, 1863, in Gettysburg, Pennsylvania, during the American Civil War. The Union Army, commanded by General George G. Meade, defeated the Confederate Army, led by General Robert E. Lee. The Battle of Gettysburg is considered a major turning point because it ended General Lee's invasion of the North and forced the Confederate Army to retreat.
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