That the world is awash in weapons is not news. But the way weapons large and small flow from the United States, Britain and other producers to the world’s villains is ever astonishing. In “The Shadow World,” Andrew Feinstein gives us a sweeping and troubling story of how this happens, who benefits, and what consequences follow.

It is troubling because we have been at it for so long — the United States has been easily the largest arms exporter in the post-Cold War era — and still can’t seem to learn the ABCs of the arms trade: (A) the weapons we produce and sell or give away very often fall into the hands of people who want to use them to shoot at us; (B) the networks of arms merchants are also attracted to other forms of illicit commerce, like nuclear materials, drugs and human trafficking; and (C) the purported benefits of sustaining the “defense industrial base” by exporting weapons are grossly exaggerated. Yet none of these sturdy facts deters policy makers of all political persuasions from pushing lethal technologies onto petty tyrants and intermittent allies in Africa, the Middle East, Central Asia and indeed just about everywhere else.

Feinstein, a South African politicianwho helped expose an infamous arms scandal involving $100 million in bribes allegedly paid to ANC politicians, writes with a crusading spirit and a depth of detail that lend “The Shadow World” urgency and authority. Many of the sensational stories he tells have earned attention before, but he adds depth and shows how often patterns repeat. The essential method of arms dealing is bribery, payoffs on a grand scale that enrich both the elites in the buying country and the arms makers in the selling country. While political agendas at times play a role in who gets what, the reigning ideology in the shadow world is greed.

The Saudis come in for a thrashing on this, the corrupters par excellence. Feinstein draws scathing portraits of Prince Bandar and Prince Turki, among other familiar figures in Washington, whose thirst for extravagance was matched only by their sheer brazenness in the arts of exploitation. For example, when quashing a British inquiry into bribery in the largest-ever arms deal, the so-called Al-Yamanah (“The Dove”) sale of British fighter jets to the Saudis, Bandar threatened to stop further purchases and intelligence cooperation if the inquiry went forward, a threat he delivered to Tony Blair at No. 10 Downing Street, saying that the cessation of Saudi intelligence cooperation would lead to “blood on the streets of London.” Blair buckled.

Less spectacular but just as consequential is the exploitation at work in antiterrorism. The meteoric growth of the homeland security state provides fresh opportunities for military contractors, who, like Lockheed, have diversified nimbly into the antiterrorism business. No one really knows how much has been spent on homeland security, but it surely approaches $1 trillion in the United States alone. For the arms merchants, the post-9/11 wars have also been, in the words of an army official quoted by Feinstein, “a feeding frenzy.” Iraq and Afghanistan have been good business not only for the usual giants of the military industry, but for many others in the darker recesses of the business.

‘The Shadow World: Inside the Global Arms Trade’ by Andrew Feinstein (Farrar, Straus and Giroux)

Feinstein reminds us briefly that the victims of the arms trade and the violence it enables are not just soldiers, but also civilians in large numbers — hundreds of thousands in Iraq and Afghanistan, the same or more in Angola’s civil war, Darfur and elsewhere. Contemporary warfare is more than ever about killing the innocent.

Regaling the reader with these misdeeds and horrid consequences, “The Shadow World” becomes a tirade, one that goes down in the weeds of dozens of deals. Feinstein has the problem that all serious nonfiction writers face, making complex and at times tedious issues understandable and compelling. For the most part, he succeeds by conveying them as stories. But it does require some work from the reader, who must navigate a jungle of actors and acronyms to follow these tales. This may be inevitable for such a comprehensive treatment of the arms trade, possibly the most complete account that has ever been written.

Feinstein makes a convincing argument that, particularly in Africa, the supply of weaponry made conflicts more lethal. It’s a powerful and sad case. Those who dismiss the notion that the arms trade is a cause of violence often point to the use of machetes in Rwanda as their example. Feinstein counters, “The popularized images of the Rwandan genocide suggest a primal orgy of slaughter, a frenzy of bloodlust and carnage. The exact opposite, however, was true. The genocide was meticulously organized in order to kill as many people as efficiently as possible. The mountains of weapons that had been imported into the country were crucial to achieving this aim” — weapons such as grenades and firearms that were used “to achieve the highest kill-rate possible.”

What he does less well is provide some hope in this stew of corruption and mayhem. A rather sophisticated if small community of experts, NGO activists and a few sympathetic governments has taken up the cause of limiting arms exports, and they met with some success with the 1997 treaty to ban land mines, a global pact (but never signed by the United States). But that was more than a decade ago, and these activists haven’t regained the traction needed to go up against the major powers — states and corporations — which cannot see past the bottom line. It may be that there’s less violence than once beset the world, as Steven Pinker argues in his new book, “The Better Angels of Our Nature,” but there’s still plenty of carnage to go around — good news for the arms makers, tragic news for everyone else.

John Tirman is author of “ The Deaths of Others: The Fate of Civilians in America’s Wars ” and is executive director of MIT’s Center for International Studies.

THE SHADOW WORLD

Inside the Global Arms Trade

By Andrew Feinstein

Farrar Straus Giroux. 672 pp. $30