Ambiguity

One reason that the invasion against the Earth is so successful is that the humans do not know what to make of it. The first Martian craft to arrive lies in the crater made by its arrival, seeming to be powerless. There is a noise from within, but that stops, leading astronomers to believe that the creatures inside have perished. When the Martians emerge from the cylinder, they are weak, gelatinous organisms, and their inability to move very freely in Earth's thick atmosphere leads scientists to believe that they do not pose much of a threat. These assumptions are based on what little information can be gleaned from the spacecraft's behavior. The Martians seem to pose no threat, until they swiftly begin their destructive attacks.

Even after the Martians prove hostile, the people of London do not see the danger facing them because the news is so sketchy...