Although it won McDougall the 1958 Governor General's Award for English-language fiction, it was his only novel, and after publishing it to wide acclaim he retreated into a quiet life as Registrar of McGill University in Montreal.

Led by the flamboyant Brigadier Ian Kildare (a modern miles gloriosus, or braggart soldier), the Canadians invade Sicily where they meet with little resistance from the Italian Army, composed mostly of hapless conscripts who want no part in the war.

The novel's main protagonist, Lieutenant (later Major) John Adam (a semi-autobiographical foil for McDougall), is an efficient soldier and leader, who nevertheless finds "the vulture fear" inhabiting his soul after the execution of the Italians.

Eventually, Adam and his men stumble on a chance to redeem themselves when one of their own comrades, Rifleman Jones, a mildly retarded but efficient infantryman, is sentenced to be executed for treason by his own army, after he falls in with a ring of corrupt soldiers who murder an American.

Like Herman Wouk's The Caine Mutiny or Leo Tolstoy's War and Peace, both of which were key models for McDougall, Execution is a novel that combines visceral depictions of combat with philosophical questions about the blurred boundaries between good and evil.

Other important themes include the abuse of military power, especially in one scene involving Allied generals planning an attack against the Germans that is bound to fail, and the isolation and alienation of front-line soldiers from mainstream society.

The movie was a typical low-budget Canadian affair, with a small dirt road in back-woods Ontario masquerading as Maple Leaf Route, and little sense of scale in terms of equipment, locations, or number of characters on screen.