The refugee flows from the Middle East, where grass-roots radicalization and arms training are widespread in the war-torn states, hold important security implications for the destination countries. Europe today is focused on the refugee crisis, with NATO instituting patrols in the Aegean Sea to intercept migrants trying to reach Greece. But in some years, Europe’s focus could shift to internal security threats.

Indeed, the director of U.S. National Intelligence Director James Clapper has warned that the Islamic State terrorist group is infiltrating refugees escaping from Iraq and Syria so as to operate in the West. According to Clapper, Islamic State terrorists are “taking advantage of the torrent of migrants to insert operatives into that flow,” adding that they are “pretty skilled at phony passports so they can travel ostensibly as legitimate travelers.”

Germany, the prime destination of the current migrant flows, welcomed around 1 million refugees last year. But unlike the roughly 3 million migrants from Turkey that came to Germany from the 1960s onward to meet the demand for labor in the booming German economy, those arriving today are from countries battered by growing jihadi extremism and violence.

The refugee exodus is just one manifestation of a deeper problem — how interventionist policies of outside powers in recent years have unraveled fragile states such as Libya, Syria, Iraq, Yemen and Afghanistan. Following World Wars I and II, European colonial powers and the United States sat around tables and redrew political frontiers in the Middle East, creating artificial new nations with no roots in history or preexisting identity.

The net effect of the latest round of interventionist policies is the emergence at Europe’s southern doorstep of a jihadi citadel that extends from the Maghreb to the Sahel, with Libya at its hub, and the rise of another jihadi stronghold in the Syria-Iraq belt. Dealing with the threats from these two jihadi citadels will challenge Europe in the coming years even more than the refugee crisis, in the same way that countries next to the Afghanistan-Pakistan jihadi belt are paying a high price in terms of their security.

In this context, the Paris terror attacks’ larger lesson should not be forgotten: Unless caution is exercised in training and arming Islamic militants in another region, the chickens could come home to roost. Jihad cannot be confined within the borders of a targeted nation, however distant, as the examples of Afghanistan, Syria and Libya indicate. The fact that French and Belgian nationals were behind the Paris attacks has shown how difficult it is to geographically contain the spread of the jihad virus.

Indeed, internal security challenges in Europe have been compounded by Western foreign policy missteps and misplaced priorities. Take the situation in battle-worn Syria and Iraq: Defeating the Islamic State is a pressing issue on which an international consensus — and coalition — can be built. But the Western-led camp first needs to get its act together, including by prioritizing the Islamic State’s eradication over regime change in Damascus and by stopping Saudi Arabia, Turkey and Qatar from aiding al-Qaida-linked militant groups in Syria and Iraq.

Even without considering the specter of Islamic State fighters hiding among innocent civilians to reach the West, the flow of refugees poses a security challenge for the countries they enter, because they are arriving from violence-scarred lands. In the refugee-producing conflict zones, the call to jihad has indoctrinated many to see violence as a sanctified tool of religion. Large numbers of men have not only received arms training but also used weapons in combat.

More than half of the slightly over 1 million refugees who flocked to Europe in 2015 were men of fighting age. So far this year, due to pressure for families to reunify, children and women have made up 54 percent of the new arrivals, according to United Nations data.

The risks from jihadi indoctrination cannot be discounted, as was highlighted by what happened in San Bernadino, California, where a married couple of Pakistani origin massacred 14 people in December.

Moreover, former combatants in a civil war — just like ground troops returning from a regular war — are prone to suffer from post-traumatic stress disorder. According to medical research, about 30 percent of the men and women who have spent time in war zones experience PTSD, which is associated with an increased risk of violence.

In this light, addressing the refugee crisis will be no easy task for Europe. Building higher fences to secure Fortress Europe cannot be the answer by itself. Refugees will do anything to escape war and chaos, including risking their lives, as they are doing by taking unseaworthy boats.

More fundamentally, how can any European nation ensure that the refugees it takes do not include radical jihadis who extol mass murder as a tool of jihad? Integrating the refugees already admitted will be a major challenge, as Germany has experienced with its Turkish immigrants, who remain poorly integrated in German society.

Let us be clear: No country can accept an unrestrained influx of refugees, because it would get swamped economically, socially and culturally, and face major political fallout domestically. The issue is how to control the migrant flow in a humane way, in accordance with international law, while admitting a limited number of genuine, properly vetted refugees.

However, there is no European or international policy on refugees. The two instruments of international law — the 1951 Refugee Convention and the 1967 Refugee Protocol — are scarcely adequate for dealing with the current refugee flows.

For Europe, the Mediterranean holds the key for its security. Yet little attention has been paid in European security policies to shoring up the continent’s southern flank. Instead, identity politics in the form of nationalism is back in Europe — a development set to accentuate internal security challenges relating to refugees.

Long-time Japan Times contributor Brahma Chellaney is a geostrategist and the author, most recently, of “Water, Peace, and War.”

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