Like ancient gaul, Colombia can be said to be divided into three parts. After several decades of undeclared civil war, leftist guerrillas dominate much of the southern part of the country. Much of the north is in the hands of right-wing paramilitary groups backed by wealthy landowners (though the leftists have a piece of this region too, near the Caribbean coast). Both the rebel insurgents and the rightist militias are involved in drug trafficking—a highly lucrative enterprise, Colombia being the world's principal producer of cocaine and a major provider of heroin. The beleaguered central government is literally central, occupying what might be called, without much exaggeration, an urban median strip.