On September 11, the British fleet came together — 50 vessels, ranging from the 80-gun flagship through 74-gun men-of-war, 38- and 36-gun frigates, to rocket and bomb ships (actually huge rafts). Transports carried "Wellington's Invincibles," the 4,000 or so troops who had so enjoyed themselves in Washington.
Early on the morning of the 12th, the redcoats landed east of Baltimore and charged the massed militia. And this time things fell apart for the British. Two American snipers quickly picked off the British commanding general, and although some militiamen skedaddled, many others stuck it out. Humid, rainy weather helped the American cause. The Invincibles pulled back and encamped, waiting for the navy to do its stuff. The ships would first have to put out of action that pesky Fort McHenry.
Next morning, in pouring rain, bomb ships opened fire thunderously from about two miles below Fort McHenry — well out of range of its guns. Mortar bombs, some of 200 pounds, soared high in the air and plunged into the fort to explode in showers of rubble. Key, Skinner and Beanes had a distant view from their small vessel. They made out a flag, limp in the soggy air.
All day the guns bellowed. Newly introduced Congreve rockets screeched toward the fort in hopes of starting fires. When enemy "bomb," or mortar, vessels moved in to score even more hits, the Americans opened up with everything they had and drove the British back.
Night fell. The tremendous bombardment eased off as boatloads of British troops slipped past the fort to attack the city. The Americans spotted the foray, and their guns roared, and again the British had to pull out of range. Desperate to finish off the fort, they redoubled their cannonade, bombs curling high in the night sky, their lit fuses streaking across it, then down to their bright burst. Key, tirelessly watching, realized that the roar of British guns meant the fort still held; by the burst of bombs he could see the flag, still there.
And, in the faintest first light of dawn, at about the time the British command called off its Baltimore campaign, he spotted it. The rain had ceased; a stirring of wind opened it, and he made out the red of the stripes, the blue square. The American flag.
As a poet, Key could be suddenly and deeply moved, and instinctively he'd create rhythmic phrases to describe his feelings. All night, words had tumbled in his head: proudly hailed...gallantly streaming...bombs bursting in air...gave proof...Still there! Now he scribbled them on the back of a letter, then later, safely ashore in Baltimore, he wrote out and polished the song. Of course it had to be a song.
The phrasing of "Defence of Fort McHenry," as he first named it, fitted perfectly an old favorite: "To Anacreon in Heaven." This was the song of a popular London gentlemen's club, the Anacreontic Society, honoring an ancient Greek poet who lyricized life's joys. Members devoted themselves to good food, good wine, good cheer. They'd composed a pleasant, lilting tune, and one of the club's presidents had supplied words, a fanciful communication with Anacreon, fun to sing:
To Anacreon, in Heav'n, where he sat in full glee,
A few sons of harmony sent a petition,
That he their inspirer and patron would be;
When this answer arriv'd from the jolly old Grecian—
"Voice, fiddle, and flute,
No longer be mute;
I'll lend ye my name, and inspire ye to boot;
And, besides, I'll instruct ye, like me to intwine
The myrtle of Venus with Bacchus's vine."