We all know about the crucifying sadists who comprise the Islamic State of Iraq and Syria (ISIS). But did you know that Australia, according to Time, is the highest contributor, per capita, to their legion of foreign fighters?

Julie Bishop says 150 Australians are fighting in Syria and Iraq while the US security expert Aaron Zelin thinks there might be up to 200. The point is that Australia’s export of jihad represents the most serious threat to our national security.

Writing in the Weekend Australian, Paul Maley and Mark Schliebs say that the convicted Australian terrorist Khaled Sharrouf is among a number of Australian jihadis who merrily performed battlefield executions of captured Iraqi prisoners for ISIS’s noble enterprise. As you may recall, Sharrouf waltzed out of Sydney Airport on his brother’s passport last year. Officials cited a ‘fairly major breakdown’ in border security, a phrase difficult to be spoken aloud except in a rather gloomy, sheepish monotone.

We have reached the point where the blowback from the huge number of foreign fighters in Syria — around 11,000, including approximately 3,000 Westerners — has moved from the realms of theory and data into the cold light of reality, as shown by the murders at the Jewish Museum in Brussels. These numbers, including Australia’s contribution, are increasing exponentially as the Syrian conflict drags on.

As hard as it is to believe, our citizens occupy senior roles in both the metamorphosis of al-Qa’eda in Iraq, ISIS, and Jabhat al-Nusra, al-Qa’eda’s official Syrian franchise. It gets worse: two of our most notable hate-preachers are playing starring roles in ISIS and al-Qa’eda, which fell out with each other earlier this year.

Take Musa Cerantonio, whom the International Center for the Study of Radicalisation identifies as one of the two most prominent spiritual authorities that foreign fighters in Syria look to for inspiration and guidance. He’s an unabashed cheerleader for ISIS from his bolt-hole in the Philippines. In a fiery sermon in Brisbane last year, he referred to Jews as ‘pigs and monkeys’, salivating over the impending destruction of the Jewish state while praising the mujahid in Syria. Or take Abu Sulayman: he implored his Australian followers to join the jihad in Syria, and occupies al-Nusra’s General Islamic Council. Both also preached out of the same infamous (and now defunct) Al-Risalah bookshop in Sydney. How on earth was this security madness allowed to take place for so long?

According to the Norwegian terror expert Thomas Hegghammer, around one in nine jihadi veterans of foreign conflicts are involved in acts of domestic terrorism that are both more likely to succeed — and more lethal when they do — than those carried out by their non-veteran counterparts. Hegghammer warns: ‘A one-in-nine radicalisation rate would make foreign fighter experience one of the strongest predictors of individual involvement in domestic operations that we know.’

And to think matters will only deteriorate if groups like ISIS, or the central al-Qa’eda leadership, decide to use the huge reservoir of Western fighters to attack external targets in the West. Congressman Mike Rogers, chairman of the US House Intelligence Committee, argued last October that terror groups are bound to turn their sights away from the Middle East and onto the West.

Syria has become the de rigueur training ground for jihadists across the globe. Not since Afghanistan has a conflict been so easily accessible to those willing to participate in it — a short drive across Europe for Brits, French, Belgians, Kosovars, Swedes, and Spaniards — or, for Australians and other jihadis not connected to the European landmass, a relatively cheap flight to Turkey, whose porous borders provide a painless entry to the Syrian quagmire.

Australia should not follow the ludicrous path of my country of birth, Britain, in allowing jihadis to roam free, in the hope of creating ‘open networks’, able to be monitored by intelligence services. The ascendancy of the ‘lone wolf’ attack, as seen with the murder of Drummer Lee Rigby last year, by a man known to intelligence services, attests to the folly of this ‘covenant of security’ approach. Nor, as the recent conviction of Abu Hamza testifies, should they outsource their response to other countries.

Dual-citizens fighting in terror organisations should have their Australian citizenship revoked, à la the work of Theresa May in the UK. Single-nationality Australians known to be fighting and assisting terror groups should be detained and tried under the Crimes (Foreign Incursions and Recruitment) Act 1978, and Criminal Code 1995 immediately upon their return to the country. The latter includes, as a spokesperson for the Attorney-General said to me, ‘directing the activities of, being a member of, recruiting for and training with a listed terrorist organisation, and/or providing funds or support and associating with members of a listed organisation’. Both Jabhat al-Nusra and ISIS are proscribed organisations, and Australians have died serving in both of them.

Efforts are already being expended to prevent Australians travelling to Syria. Police arrested an alleged recruiter for Jabhat al-Nusra, Hamdi Alqudsi, in December last year. ASIO have been cancelling and withholding passports at a continually increasing rate. Shiraz Maher, speaking of Britain, suggests ‘a legislative approach which establishes clear procedures and allows for judicial oversight’ and ‘robust measures to stop and prosecute potential suspects before they leave this country’.

We might also do well to take another hint from the Motherland. The Quilliam Foundation’s suggestion that rehabilitation be used as an off-ramp for returnees would help reintegrate those non-violent Australians, in Syria for broadly humanitarian reasons, who have invariably been exposed to jihadist indoctrination. Such a programme would need to be implemented immediately as Australians begin to return from the conflict.

Australians run the risk of treating the involvement of fellow citizens in the Syrian conflict with equanimity. This is a grievous mistake. Radicals affect the integrity and stability of their host communities before affecting wider society. Alas, the end-point of the latter is all too familiar in the West.