The War of the Worlds often includes ominous foreshadowing of future events. For example, the first line of Book 1, Chapter 1 foreshadows the arrival of intelligent aliens on Earth:
No one would have believed in the last years of the 19th century that this world was being watched keenly and closely by intelligences greater than man's and yet as mortal as his own.
This line buries the lede about alien life by discussing people's reasonable doubt that it exists. However, this doubt turns out to be anything but reasonable. The narrator insists that humanity's hubris caused it to assume the planet's safety (and subsequently made it vulnerable to attack). He admits that the Martians have intelligence that is "greater than man's" and that this is what allowed them to wreak havoc on earth.
This line also foreshadows two important points about the story. The first point is that the world is being "watched keenly" by the Martians in anticipation of an invasion. The second point is that the aliens—despite their advanced technology—are "as mortal as humans" and will eventually die of a simple bacterial outbreak against which they lack immunity. Wells does not aim to deceive the reader; rather, he presents information in a linear, straightforward fashion and does nothing to hide his characters' impending fates.
Early in the novel, Wells hints at the aliens' eventual death from earthly bacteria. This point suggests that all creatures, no matter how advanced they seem, are vulnerable in their own way. In Book 2, Chapter 2, the narrator mentions that Mars lacks microorganisms, which foreshadows the Martians' eventual downfall:
The last salient point in which the systems of these creatures differed from ours was in what one might have thought a very trivial particular. Micro-organisms, which cause so much disease and pain on earth, have either never appeared upon Mars, or Martian sanitary science eliminated them ages ago. A hundred diseases, all the fevers and contagions of human life, consumption, cancers, tumours and such morbidities, never enter the scheme of their life. And speaking of the differences between the life on Mars and terrestrial life, I may allude here to the curious suggestions of the red weed.
The phrase "what one might have thought a very trivial particular" recalls the novel's first line, in which the narrator states that "no one would have believed" in intelligent extraterrestrial life, let alone an invasion. The narrator often insists that what people believe to be true will turn out to be false. Here, he hints that the absence of such bacteria on Mars is not so "trivial." The Martians, much like the humans, seem to think they are invincible. Both groups are wrong—earth has been invaded, and the Martians die of a basic bacterial infection. What ultimately determines survival is not technological advancement but a biological advantage. The Martians' downfall due to lack of immunity recalls Darwin's Theory of Evolution, as the aliens cannot win the contest of "survival of the fittest" on earth because they lack the necessary immune function. Foreshadowing permits insight into the Martians' eventual demise and emphasizes that the key to survival is a biological advantage.
