The marines. [Not to worry, Aang. While she doesn't have the same trigger points, it's a little unnerving for weather to be ruined permanently by the power of a couple people fighting, for a weather geek like Nami.] It's...a complicated story and won't make much sense if you're not familiar with our history. They did choose a tiny and uninhabited island for it, which had been supposedly impossible to live on beforehand anyway.

[...] Mostly uninhabited. There was a lab there.