What are the themes in The War of the Worlds?

Nineteenth-century science fiction often focuses upon man's ability to achieve things beyond the scope of what had been thought possible in the pre-technological, pre-industrial age. Jules Verne, for instance, presents fantastic scenarios that extend both outward, to space (in From the Earth to the Moon), inward (Journey to the Center of the Earth), and everywhere, so to speak, in Twenty Thousand Leagues Under the Sea and Around the World in Eighty Days. H. G. Wells's fiction, while continuing these predictions of achievement, generally has much darker themes than that of Verne. In The War of the Worlds, the principal idea is that of humanity's vulnerability, his weakness in the face of a "futuristic" technology, but one in the hands of ruthless and (at first) seemingly all-powerful aliens.
The message in Wells is not only one focusing on the possibility of humanity's destruction, but also one that debunks the traditional notion of humanity as the "center" of the universe, presumably the only intelligent being in creation. The implication, although a secondary one, is that humanity can destroy itself if it eventually comes to possess the kind of technology the aliens have. Within less than twenty years of his writing The War of the Worlds, poison gas came to be used by the European powers in World War I. This is essentially the same thing as the "black smoke" Wells depicts the Martians using to wipe out humans. Much has been discussed about Wells's novel as an allegory of European imperialism, and there is some truth in this. However, in my view, it is more the general theme of the exposed, essentially defenseless nature of any beings that his novel centers upon. The aliens herd and feed off of humans in the same way humans herd and feed off of animals.
Though Wells's emphasis is different from that of his predecessor Verne, the earlier writer also expresses the darker concept of the potential ruthlessness and amorality that seems to go hand in hand with intelligence and technology. In Twenty Thousand Leagues Under the Sea, Captain Nemo is a megalomaniac, viewing himself as possessing a kind of godlike power over other men. In The War of the Worlds, it's the aliens who appear to have the godlike power until they are brought down by nature, by the microorganisms to which they have no immunity. It is a completely random outcome, perhaps meant by Wells as emblematic of the overall randomness that governs the world, in spite of humanity's pretensions to being in control of our fate.