Vollmann reports from two places where violence had settled into routine. The first is Mogadishu during the American intervention, riding out at night with a Marine squad ordered to confiscate weapons from every faction impartially, led by a corporal who says the frightening thing is never knowing where the enemy is. A man from another platoon is shot on a street they had patrolled that afternoon; a newspaper clipping notes the United Nations withdrawing convoy protection a year later.

The second is the Muslim south of Thailand, where he tries to determine whether the separatist bands are fighting for Pattani and Islam or running extortion rackets, and finds the distinction will not stay put.

The method is deliberately unresolved. First-person narrative is broken up by flat transcripts, a provincial governor, a defector, schoolgirls, low-ranking policemen, an ageing separatist leader, set against each other rather than reconciled.

Reporting, not theory, carries this volume. Vollmann travels through Cambodia and the Thai border zone in the years after the Vietnamese withdrawal, and his method is to let people account for their own violence and then set the accounts against each other.

In Phnom Penh he visits Tuol Sleng and the killing field at Choeung Ek, an amputee rehabilitation centre, and the mined road north to Battambang, where a provincial commander briefs him for an hour before he can ask a question and a commune committee meets beside a dugout roofed with logs to soak up shellfire. Across the frontier he tries to buy his way toward the Khmer Rouge and the logging money that sustains them, and hears from a brothel owner and a smuggler's sister why the movement was not, in their telling, so bad.

Japan's yakuza appear on the same terms: extortionists entirely convinced that they protect the weak.

This volume distils the argument of the larger work into a numbered code. The principles, Vollmann explains in a prefatory apology, were extracted wherever possible word for word from the four theoretical volumes that precede it, and are offered as working rules rather than as an exact science of ethics.

The structure is that of a legal instrument. It begins with how to form a moral code, variations on the Golden Rule, and maxims addressed to murderers and tyrants, then runs through a long sequence on when violence is warranted, when it is not, and when it is inexcusable yet forgivable. Categories of self-defence extend from honour and race through homeland, ground, earth, animals and gender to defence against traitors and defence of revolution; a second section treats violence as policy, covering deterrence, retribution, revenge, punishment, obedience and sadism.

Each rule carries caveats, cross-references and worked examples, from Bernhard Goetz to the Talmud.