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."
"No. They just really mess them up. It goes into their body really easily and it's super carcinogenic, permanently fucks their DNA up, basically eats their skin, probably causes them to go blind, and will make them mentally fucked up. But it takes hours for them to notice the effect."
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.