Helping combat ISIL means a dramatic, full-scale effort to help our fellow NATO member state — Turkey — secure its border with Syria , monitor and control the people crossing that border and help our Turkish ally forestall any future spillover of the Syrian conflict onto its own territory. This all should be seen as consistent with NATO’s obligations to an important member-state.

Yes, it would be an unusual mission for NATO, but not more so than other tasks the alliance has undertaken in recent years, including in Afghanistan, where most of NATO’s activities for the past 12 years have not involved war-fighting. NATO’s primary objective in Afghanistan was to enable the Afghan authorities to provide effective security across the country and ensure that the country can never again be a safe haven for terrorists. A NATO mission in Turkey would not be greatly dissimilar, and it would enjoy an additional clarity of purpose in that it is helping an alliance member enhance its security on the edge of a major conflict….

A robust NATO mission focused on the Turkish-Syrian border would resolve those problems. It would come with a joint intelligence cell that could provide the information and cooperation needed to monitor and control the flow of would-be jihadists from throughout Europe and, perhaps even more important, on their way back home after serving the ISIL monster. And it would come with the deployed forces to enhance Turkey’s own ability to seal that border against nefarious traffic that makes the struggle against ISIL so challenging.

Most sources now estimate that at least 20,000 foreign fighters have flowed into Syria, mostly across the Turkish border. These include an estimated 2,500 citizens from key allies Germany, France and the United Kingdom, likely all transiting through Turkey into Syria. Just in recent days, we’ve seen authorities issue alerts for three teenage British girls who are believed to be transiting through Turkey to fight with ISIL in Syria….

The importance of the 350-mile Turkish/Syrian border will remain critical until we get it under control.

That border is not just between Turkey and the open wound that is Syria; it is between Syria and all of Europe; it is between Syria and NATO. The alliance should meet this challenge as the most urgent of this young century.

Dan Coats is the senior senator from Indiana and a member of the Senate Intelligence Committee.

Image: NATO Secretary General Jens Stoltenberg visiting the US Patriot unit deployed in Turkey, Oct. 10, 2014 (photo: NATO)