In "The Star-Spangled Banner," what "gave proof" in line six? Twilight, bombs, mailed, stripes and stars, or the dawn's early light.

The first lines of the first stanza of the national anthem pose
the question about whether the American flag is still visible flying above Fort McHenry in
Chesapeake Bay. Author Francis Scott Key witnessed the War of 1812 naval Battle of Fort McHenry
from a British ship where he was temporarily being held prisoner. He was unable to determine who
was winning the battle, but he realized that as long as the American flag was flying above the
fort, there had been no American surrender. In the sixth line, the "proof" that is being shown is
the visibility of the American flag above the fort. Key could not have seen the flag in the total
darkness, but the "rockets' red glare" and "the bombs bursting in air" lit up the sky enough for
Key to see that the flag was "still there."