The War of the Worlds, by
H.G. Wells, is a classic science fiction tale of Martian invasion. The story is narrated by a philosopher who lives a quiet life in the English country with his wife. When visiting an astronomer friend at his observatory one night, they witness what would seem to be shooting stars, but for the fact that they appeared to have been fired directly from Mars. It is not too long before a large metallic cylinder comes crashing into the earth near their homes. The news gets out of course, but no one is alarmed at first, since it takes a rather long time for the martians to emerge from their cylinder, and once they are out, they don't appear to be capable of leaving the crater their vessel made. Their sluggishness and apparent immobility is attributed to their not being able to adjust to the additional gravitational force on this planet, and everyone feels quite safe because of it.
Up until the martians finish constructing their deadly heat ray, that is, and begin burning to death everything within its range.
This unfortunate turn of events is...well...unfortunate. But they still can't get out of the crater, right? So as long as you're not in range of this heat ray, you're safe.
Except then it turns out the martians have also brought along things to put together humongous death machines to roam about the countryside in, burning up stuff with their heat rays and snatching up people to feed upon, and causing a widespread general panic. The military of course was called in, but this is the late 19th century, so their weapons are obviously no match against the superior technology of the martians. Humankind is pretty screwed, yeah?
Maybe, maybe not.