Final answer:
The phrase indicating the significance of Gettysburg discusses the aftermath of Pickett's Charge and its role in making it the battle with the highest casualty rate, marking the last Confederate attempt to invade the North.
Step-by-step explanation:
The phrase that best supports the answer about the significance of the Battle of Gettysburg can be found in the detailed description of Pickett's Charge, where it is stated, "Half the men who made Pickett's Charge were wounded or killed in the action, helping to give Gettysburg the highest casualty rate of the war... Gettysburg marked the last time Lee would attempt to invade the North." This part of the text underlines the high costs of the engagement and indicates the crucial turning point it represented in the Civil War. The immense scale of loss and the tactical consequence of restraining Lee's offensive movements are highlighted, supporting why Gettysburg was a pivotal battle for the Union.
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