Besaslan, Turkey (CNN) - On the southern edge of Turkey, rolling brown pastoral hills slope gently to the Syrian border, with small towns like this one dotting the horizon. The calm on this side of the border, however, belies the scene on the other side.
Just across the border in northern Syria, the Islamic extremist group known as ISIS is fighting a full-tilt battle in its effort to capture and control new territory, part of its push to create a sprawling Islamic caliphate, or separate Islamic state, modeled on the first caliphate that spread across the region in the centuries following the death of the Prophet Muhammad around 640 AD.
As ISIS fighters expand their control, it is in the border region, in villages like Besaslan, where the Islamic State group can make some of the money it needs to finance its wars. Oil-smuggling operations involving millions of barrels have recently been uncovered.
The oil comes from wells and refineries that ISIS has taken over inside northern Iraq and northern Syria, and until very recently it was easy to smuggle it into this quiet part of southern Turkey. One reason is that cheap, smuggled oil is a much-prized commodity in Turkey, where oil is so expensive that it almost doesn't matter who is selling it, even if it's your enemy.