So the United States has brokered a cease-fire among the warring factions in Darfur, and the U.N. Security Council has authorized the deployment of a peacekeeping force. To anyone blissfully unfamiliar with history, this sounds like a decisive step that will finally end the violence that has left at least 200,000 dead and 2 million homeless.

Alas, this is not the first cease-fire agreement in Darfur.

An accord was reached in 2004 and was immediately violated. There is no reason to think that the current treaty will fare any better, especially because one of the main Darfur rebel groups has refused to sign it.

Pieces of paper, no matter how promising, require power to be enforced.

The question is: Who will provide that power in Darfur? The African Union force deployed in 2004 has proven woefully inadequate. Its 7,000 soldiers lack the numbers, training and equipment to patrol an undeveloped region the size of France. They don't even have a mandate to stop ethnic cleansing; they are only supposed to monitor the situation.

If you listen to the bloviators at the U.N., salvation will come from the deployment of a larger corps of blue helmets. If only. What is there in the history of United Nations peacekeepers that gives anyone any confidence that they can stop a determined adversary?

The odds are much greater that U.N. representatives will instead be taken as hostages by bloodthirsty thugs, as happened in Bosnia-Herzegovina in 1995 and in Sierra Leone five years later. Or that rather than protecting the people, the peacekeepers will prey on them — as allegedly has happened in Kosovo, Sierra Leone, Liberia, Guinea and Congo, all places where blue helmets have been accused of a horrifying litany of sexual abuses, including pedophilia, rape and prostitution.

Even if these worst-case scenarios don't come to pass, the U.N. is likely to prove ineffectual in the face of determined opposition. Look at what is happening in East Timor, where, after seven years of U.N. stewardship, the capital has been paralyzed by fighting among armed gangs. The situation is even worse in Haiti, where a Brazilian-led U.N. force has done little to stem growing chaos. It is worse still in Somalia — the most lawless country on Earth — where a U.N. deployment failed in the early 1990s.

And to think that some self-described realists had the temerity to suggest that everything would have worked out in Iraq if only the lead role had been turned over to the U.N.! East Timor and Haiti are much smaller and more isolated, but the U.N. hasn't worked its multilateral magic in either place.

My point here isn't to indulge in U.N.-bashing for its own sake but simply to suggest that we should temper our expectations for the peacekeeping force that is due to arrive in Darfur in six to nine months' time. The drawn-out timetable itself suggests how ineffectual the U.N. is. Even under the best of circumstances, the "Janjaweed" militia will enjoy another half-year of rapine without serious interference.

If the so-called civilized nations of the world were serious about ending what the U.S. government has described as genocide, they would not fob off the job on the U.N. They would send their own troops. But of course, they're not serious. At least not that serious.

But perhaps there is a way to stop the killing even without sending an American or European army. Send a private army. A number of commercial security companies such as Blackwater USA are willing, for the right price, to send their own forces, made up in large part of veterans of Western militaries, to stop the genocide.

We know from experience that such private units would be far more effective than any U.N. peacekeepers. In the 1990s, the South African company Executive Outcomes and the British company Sandline made quick work of rebel movements in Angola and Sierra Leone. Critics complain that these mercenaries offered only a temporary respite from the violence, but that was all they were hired to do. Presumably, longer-term contracts could create longer-term security, and at a fraction of the cost of a U.N. mission.

Yet this solution is deemed unacceptable by the moral giants who run the United Nations. They claim that it is objectionable to employ — sniff — mercenaries. More objectionable, it seems, than passing empty resolutions, sending ineffectual peacekeeping forces and letting genocide continue.

Max Boot is a senior fellow at the Council on Foreign Relations. He wrote this commentary for the Los Angeles Times.