How does the structure of the "The Star-Spangled Banner" emphasize its main idea?

The Star-spangled banner, the National Anthem of the United States of America is a poem inspired by the Battle of Baltimore, fought on September 12-14, 1814 during the War of 1812. During the British campaign against Washington, D. C., an elderly and respected physician, Dr William Beanes was arrested for unfriendly acts toward the British soldiers which resulted in his arrest.

Francis Scott Key, a prominent lawyer and friend of Dr Beanes was sent by President James Madison to obtain his release. Following negotiations, the British agreed to release Beanes. However, since the British were going to attack Baltimore, Maryland next, they would allow no one to go ashore.

The British landed soldiers on September 12 and engaged in a brisk land battle, however, they were not able to capture Baltimore. As part of a two-pronged attack, the British now sent their naval fleet to attack and destroy the port city. The main defence of Baltimore harbour was Fort McHenry. For 25 hours the British fleet fired rockets and bombs at the fort.

The fort's defenders bravely withstood the bombardment and did not surrender. The British realized they could not take Baltimore without paying for it with heavy casualties. Since they were not willing to pay this price, they departed from Baltimore.