Final answer:
The line about the rockets' red glare in the American national anthem was inspired by the British bombardment of Baltimore during the War of 1812, as witnessed by Francis Scott Key.
Step-by-step explanation:
The line about the rockets' red glare in the American national anthem was inspired by the War of 1812, specifically by the event of the British bombardment of Baltimore. During the fierce battle, Francis Scott Key witnessed the bombardment and was moved by the sight of the American flag's survival the next morning.
His poem, 'In Defense of Fort McHenry,' which later became 'The Star-Spangled Banner,' encapsulates the volatility and resilience seen in the battle where the rockets provided the only illumination over the fort, proving the American flag was still standing. This powerful imagery is what we now sing about in the national anthem, reflecting the pride and tenacity of the American spirit during that era of war.