As Timothy Findley’s novel explores the lives of soldiers during World War I, its primary theme is the limited usefulness of war in solving human problems. Instead, the experience of service seems to destroy as many people as it saves. The novel’s title of The Wars, plural, implies that the Great War is not the only large conflict that affects the protagonist, Robert Ross, and those close to him. Each person who goes off to war fights their own emotional and mental battles; and the same is true, albeit in different ways, for those who remain on the home front.

The complexities of family love are another important theme, as Robert’s complicated love for his sister and his devastation after her death shape his decision to enlist and, in so doing, withdraw his physical and emotional support from his parents. Animals play key roles in the novel, thematically linking the innocence and purity of animals to people's devoted care for them—or the calculated cruelty of Robert's parents when they order Robert, and then Teddy Budge, to kill the pet rabbits.

As an anti-war novel, Findley’s work shares themes with similar works that treat the era, notably All Quiet on the Western Front. But writing almost 60 years after the Great War ended and from a Canadian perspective, political themes of nationhood and anti-colonial resistance also enter the work. Through the character of Robert’s mother, several challenges to patriotism are introduced. The gruesome carnage that Robert manages to escape and the nobly-inspired efforts that spectacularly backfire are both examples of extravagant waste of human and animals lives that happens in wartime conditions. For Canadians, who are not fully British and do not lose their colonized status through service, questioning their involvement in that specific war goes further than criticizing war in general, as imperialist expansion was both a cause and consequence.