Entering the 21st century, we still have a lot of medieval politics being practiced in many parts of the world. Mostly, there are warlords. This is nothing more than an enterprising individual who has managed to raise an army of his own. It doesn't have to be a really big army, just large enough to defeat, or frighten away, anyone else's army. Thus equipped, the warlord goes into business, for a warlord is essentially a businessman who turns heavily armed muscle into money. If you have the only army in the neighborhood, your word is law and your needs are promptly attended to. It's no wonder so many people want to become warlords. This technique is thousands of years old, and it still works. Modern warlords are clever fellows and, like their ancient predecessors, dream up new scams to suit current conditions. They now know how to work the media, aid organizations, clueless peacekeepers and whatever passes for central government in their part of the world. Warlords often have other warlords as competition, and .this can produce a wild west atmosphere. Somalia, Afghanistan and Chechnya are current examples of warlords at work. In Afghanistan, the religious warlords (the Taliban) have most of the usual warlords on the run at the moment. But don't expect peace to break out anytime soon, for Afghanistan has lived with warlords for thousands of years. Same situation in Somalia, except there is no one likely to get the warlords organized and bring peace to the land. Chechnya has the Russian army trying to crush the warlords. The Russians have done this before over the past two centuries. But the warlords always come back, eventually.
Even if you manage to disband the warlord armies, you find that former "soldiers" were often little more than bandits and gangsters. Warlords can't be too choosy when putting their army together and the ranks are filled with whatever riffraff can be found, and controlled with the promise of loot, fear and freedom from prosecution. Many national armies use the same recruiting practices. After the Soviet Union fell, it was discovered that the Soviet secret police (KGB) used criminal gangs for dirty work. With the KGB gone, the "Russian Mafia" flourished, now that they didn't have the KGB to provide some degree of control. Other national armies are little more than gangsters pretending to be soldiers. It's also quite common for rebel organizations to turn into criminal gangs after the local despot, or foreign invaders are gone. Thus the Italian mafia had it's origins in a patriotic movement fighting French (and other) invaders of Sicily and southern Italy. Same thing happened to the Irish Republican Army, which, like many rebel groups, used robbery, extortion and other scams to finance their rebellion. South American and Asian rebel movement are fond of kidnapping these days.
So what is a peacekeeper to do when dealing with rebels who's regular gig is drug smuggling, or opposition political parties whose idea of fund raising is extortion and prostitution? How do you settle a civil war when the primary beef is who gets to control the diamond mines? Thus far, the attitude has been to downplay the criminal element and make whatever deals can be made to quiet things down so the peacekeepers can depart with their reputations intact. That rarely works, as peacekeepers worldwide are discovering. The hard way. The UN has tried to deal with this angle by bringing in policemen. But effective policing depends on knowing the people you are policing. This is hard to do if you don't speak the language. And the UN has had a hard time getting cops from member nations for duty in troubled areas. Moreover, many nations are reluctant to send their best policemen on what many consider a fools errand. So an inadequate number of second rate cops are sent to police people who speak a different language, have different customs and have more firepower than anything the foreign constable ever had to face back home.
Another solution is to disband the corrupt local cops (assuming there are any local police left at all) and train a new force in kinder, gentler and more effective policing methods. This has proven difficult. War torn areas usually have a tradition of corrupt policemen that is hard to stamp out. The new recruits often forget their training once they hit the streets. If anything, they learn how to play the game of pretending to be straight while shaking down everyone in sight. New cops don't mean clean cops.
What has worked in the past, but is not as acceptable today, is the old colonial methods. Basically, you take over the local government completely. You bring in your own people for long tours of duty (5-10 years or more) so they can learn the local language and customs. The outsiders run things and carefully groom junior civil servants and police and never let them slip back into the bad old ways. After a generation or so of this, you have cleaned things up and can go home. It's expensive as hell, though, and one reason the European countries eventually wised up and dumped their colonies. But it works, if you can afford it.
Warlords, Bandits, Gangsters and Rebels; Right now, there are several dozen nations suffering through civil wars, rebellions and general unrest. There is much enthusiasm for sending in peacekeeping troops and police to calm things down. What is forgotten is that we are not dealing with wars in most cases, but heavily armed gangsters. Oh, you could say that most wars are about money or real estate. Japan wanted China and Germany wanted Lebesraum ("living room") in World War II. But the current crop of patriotic mobsters are rather more crass than Hitler or Tojo. Moreover, many of the current wars are taking place in areas where there was never much government (central or otherwise) in the generally accepted sense. Africa is torn apart by tribal loyalties, which count for more than national unity when the chips are down. Places like the Balkans and Chechnya have historically been finely divided into a patchwork of clans, causes and criminal gangs who never got along well with each other.