The Strength of Nature
Relentless invaders from Mars destroy all opposition. It seems that nothing can stop this invasion since human weapons are no match against Martian technology. Nothing, it seems, can possibly stop the alien invasion from a comprehensive annihilation of mankind. And then, suddenly, as if by a miracle, the enormous tripods topple over with the Martian controller inside dying. Remarkably, the human race is saved only by the mercy of some of the tiniest creatures on the planet: bacteria. The Martian invaders have no natural immunity to Earth microbes, and so they perish of disease. This evokes the power of nature: Martians, as the ultimate outsiders, are powerless to eradicate the established natural balanced of life on our home planet.
Imperialism
The Martians may seem like mere killing machines with no purpose, but Wells makes it clear that they are attempting to conquer Earth and establish a new home after environmental changes rendered their native planet uninhabitable. This parallels the actions taken by British troops in the 18th and 19th centuries, when they conquered lands in Asia, Africa, and the Americas, killing or subjugating the native populations. In Wells' story, it is the British themselves who are conquered by a foreign power seeking to exploit their homeland.
Fear of Invasion
The first few chapters of Wells' novel are filled with foreboding: something terrible is coming and something awful will happen to the people of earth. When the cylinders begin landing, most people on earth treat them as an amusement—up until the Martian tripods rise out of them and start terrorizing the British countryside.
Like other themes, this suggests the innate fear that others might try to conquer the British, who have conquered so many other people.
The Weakness of Religion
When the narrator encounters the curate, he hopes that this spiritual leader will help him to find some sort of reason in the midst of chaos. However, the curate proves to be a coward whose impulsiveness results in his death at the hands of the Martians. This suggests that religion is no help during times of true crisis and that religious sects may not possess the kind of cosmic know-how many expect to be fundamental to their organizations.
Scientific Discovery
Science fiction gains its name from the fact that scientific ideas, techniques, or practices are central to the stories of the genre. In War of the Worlds, it is the sudden threat of Martian invasion and their advanced technology that drives the story forward. Scientists and journalists are the first ones to notice the strange explosions on the surface of Mars, but their warnings fall on deaf ears. Moreover, it is the Martians' far-advanced technology that enables them to conquer Earth so easily.
The novel ends with human scientists sorting through the wreckage of the Martian ships and leaves open the possibility that humans will either utilize these technologies to gain unprecedented prosperity, or they will harness these awesome destructive devices to use against other humans in warfare. It is clear that scientific discovery is a boon, but its powers may be used for ill as well.
Collapse of Society
Although the people of England are initially either curious about or indifferent to the arrival of the cylinders, the Martian attack quickly causes society to collapse. People flee their homes or loot stores in advance of the Martian tripods, and social structures such as the army or government quickly crumble in the onslaught of the invasion. After the collapse of society, people show their true colors: some, like the narrator, simply seek to survive, while others like the curate are too paralyzed by fear to function.
Social Darwinism and Evolution
Darwin’s theories on natural selection were quickly applied by some commentators to human societies. Although social Darwinism was denounced by Darwin himself and many other prominent scientists, the idea that superior genes resulted in social success was a popular idea. In the novel, Wells illustrates what would happen if an invasive species from another planet farther along on the evolutionary timeline came to earth. A pervasive theme running throughout War of the Worlds is the fear of how a seemingly inferior species could possibly hope to hold its own against a genetically-advanced invader. However, the fact that the Martians, despite their advancements in weaponry and warfare, prove inferior on the issue of biological adaptability is a direct challenge to this anxiety.