Why is it”the tide turned at Gettysburg”?

The Battle of Gettysburg turned the tide against the Confederacy and was a moment when Americans could glimpse an imminent end to slavery. ... There was “Howie Felterbush,” “Petty McGroin,” and “Colonel Francois de le Merde,” presumably a Franco-American from New England.

roosevelt believed that in light of the country's recent military successes, it was unnecessary to use force to achieve foreign policy goals, so long as the military could threaten force. this belief, and his strategy of “speaking softly and carrying a big stick,” shaped much of roosevelt's foreign policy.