The third verse is expressing this sentiment: "neither a hired hitman or a person forced into attacking us will win. They will both meet a gloomy end while the banner continues to wave triumphantly over any and all who oppose".

Its a very grim reminder of the horrors of war. It took a lot to create the nation of America. It was very costly to also bring about the freedom of all people. America set a precedent for the rest of the world to follow.

A good rendition: https://youtu.be/N_lCmBvYMRs