We invented the flame thrower. I know George Carlin did the bit best but… Imagine explaining that to a group of aliens.
“You… you throw what now?”
“Flames, bro.”
“For what purpose…?”
“Well, We had these people called Nazis and they liked to hide in concrete fortifications so we figured the best way to make them not be in there would be to fill it with fire.”
“Does that not harm these ‘nazis’?”
“Oh yeah, it harms them. That was like, a bonus.”
“Well, It was nice meeting you. Goodbye forever.”
… however, flamethrowers were fielded by the Germans first, and already in the previous World War.
Uh, you ought to read about what the British did in that war. They hid a bunch of massive, buried pop-up flame throwers in no-man’s land and used them to cook a bunch of Germans.