How is the title Anthills of the Savannah relevant to the novel?
In nature, an anthill represents a remarkable collective achievement in which a large group of little creatures comes together to build something that will endure. It's not surprising, therefore, that Achebe should use this striking metaphor for the title of this book. For the story is primarily concerned with the efforts of the civilian government of Kangan and its people to build a lasting democracy in a country scarred by the legacy of colonialism and military dictatorship.
The thing about anthills, though, is that they're always vulnerable to being destroyed by much bigger, more powerful creatures than the ants who built them. In Kangan, such creatures are represented by the supporters of the former dictatorship. They're determined to destroy the "anthills," those structures of democracy put in place since they were overthrown, and return to power.