Footfall

Warning: Plot details follow.

The book depicts contact between Humanity and an alien civilisation called the Fithp which has travelled to our solar system from Alpha Centauri in a large spacecraft driven by a Bussard Ramjet. The aliens are intent on military conquest of Earth.

Like several of Niven and Pournelle's books, Footfall is perhaps most notable for the imaginative alien species. Physically, the Fithp resemble small elephants with multi-digit trunks. They possess much advanced technology, but developed little of it themselves. In the distant past of their planet another species was dominant, with the Fithp existing as animals, perhaps even as pets. This predecessor species badly damaged the environment of their planet, rendering themselves and many other lifeforms extinct. They left behind their knowledge inscribed into large stone cubes, and it is from these that the Fithp have gained their technology. This plot device rather conveniently allows the Fithp to have the super-technology interstellar Bussard ramjet for their spacecraft whilst being limited to still advanced but much more mundane weapons and other technology; laser cannon, projectile rifles, small meteorites strikes to bombard surface targets, etc.

The Fithp are herd creatures, and have a strong cultural bias against coexisting peacefully. Throughout their history, when two herds meet they fight until one establishes dominance over the other and turns them into slaves. The Fithp expect their contact with Humans to proceed along these lines, and are genuinely confused by Human attempts at peaceful contact.

The novel's many characters fall into two major groups, those on Earth and those who are taken aboard the Fithp spaceship as captives. Various civilians are used to show the effects of the war on day to day life in the USA, whilst military and government personnel are used to show us a more strategic overview of events. Amusingly, a group of science fiction writers are hired by the government as technical advisors on alien technology and behaviour; many of these characters are based on real writers, including "Bob Anson" who is clearly based on Robert Anson Heinlein.

After their initial assault the Fithp land ground forces on Earth, but these are defeated by a combined Russian and American nuclear attack. It is during this initial invasion that all of the captives are taken. These also comprise a mixed bag of civilian and military personnel; a US senator, Russian Cosmonauts, an elderly couple from the US bible belt, a mentally ill woman, etc. These are put to work by the Fithp, who expect them to integrate themselves into the herd. Naturally the Humans decide to co-operate until a chance for some serious sabotage presents itself.

The Fithp respond to the defeat of their invasion by dropping a "dinosaur killer", a large asteroid whose impact results in environmental damage on a global scale. In the aftermath the aliens invade Africa, where they enjoy more success.

The United States responds by beginning a project to build "Michael", a large heavily armed spacecraft propelled by nuclear explosions (a real drive system concept commonly known as project Orion). Michael eventually launches to intercept the alien spacecraft in a battle which conveys a remarkable sense of excitement and realism. The end of the book sees the Fithp accepting that Humanity is the stronger species and surrendering themselves to become part of the Human "herd".