Understanding which battle qualifies as both the deadliest by total casualties and a turning point helps connect how losses shape momentum in a war. Gettysburg, fought over three days in July 1863, produced about 50,000 casualties in total, the largest toll of any Civil War battle. That huge cost, combined with its strategic outcome, marks it as a turning point: it halted Lee’s invasion of the North and shifted the momentum to the Union, boosting Northern morale and signaling that Confederate hopes of winning on Northern soil were diminishing. By contrast, Antietam had the war’s bloodiest single day, but the overall casualties for the battle were lower than Gettysburg, so it isn’t the battle with the largest total losses. Fredericksburg was a costly Confederate victory with heavy Union losses but didn’t change the war’s strategic direction. Vicksburg was decisive in controlling the Mississippi and is a turning point in the Western theater, but its casualty total isn’t the largest. So Gettysburg best fits both criteria: the greatest total casualties and a clear strategic turning point in the war.