The first defeat for the alleged killers of James Foley would be for him to be remembered as a courageous journalist. Reporting from a war zone is riskier than ever: over 200 media workers died in the Iraq war, more than any other conflict; at least 70 journalists were killed in global conflicts last year; and Agence France-Presse estimates that at least 30 have died this year. Foley had already spent 44 days in captivity at the hands of Gaddafi’s forces in Libya, but that did not deter him from seeking to uncover the truth about Syria. His apparent killers want him to be remembered as a tool to spread terror; celebrating his work would be an act of defiance.

Everything about the video seemingly of Foley’s murder is intended to chill. It is unlikely that Islamic State (Isis) selected an executioner with a strong London accent for no reason. It was the Iraq war that first popularised the execution video, but hearing the blood-curdling threats and dogma of Isis recited in tones that are all too familiar is itself a message.

Terrorism by definition aims to spread terror to achieve its political ends. One of the reasons Isis has outmanoeuvred its rivals is because it has embraced social media so effectively. By publicising its atrocities online, it tells would-be opponents what will happen if it is resisted, and this partly explains why so many have fled rather than confront Isis forces. The ruthless use of social media has proved instrumental in the toppling of entire cities. This operation is being gladly assisted by those in the west who portray Isis as a unique, undiluted evil that needs to be bombed out of existence, granting the militant group the mystique it clearly craves and relies on.

Foley’s murder will inevitably intensify calls for further western military involvement. Those agitating for such a course of action have a number of questions to answer. The “war on terror” began 13 years ago. It has involved bombs raining down on Afghanistan, Iraq, Pakistan, Somalia and Yemen. And with what success? Jihadism is stronger than ever; Isis is not only more extreme than al-Qaida, but what it has achieved surely exceeds Osama bin Laden’s wildest ambitions. Who can deny that the west has served as a recruiting sergeant for Islamic extremism, that it effectively helped hand large swathes of Iraq and Libya over to such elements?

Nobody is pretending that Isis is going to be defeated by a few rousing renditions of Kumbaya. But Isis strategists must surely crave further western military involvement. As the Norwegian terrorism expert, Thomas Hegghammer, put it: “Isis seems to be doing everything it can (short of attacks in the west) to draw the US into the conflict.”

Richard Barrett, the former head of counter-terrorism at MI6, warns current military action could play into Isis’s hands. In Iraq, the sectarianism of the former prime minister, Nouri al-Maliki, helped fuel Sunni resentment that Isis fed on; his departure offers at least hope of a unity government that can peel away those sections of the Sunni community who do not like Isis but fear the alternatives even more. Surely only then can the Iraqi military hope to defeat these sectarian murderers. As for Syria: well, it is no longer far-fetched to imagine a rapprochement between the west and the Assad dictatorship.

The counter-history favoured by supporters of western intervention is that these are the grim consequences of failing to support “moderate” Syrian rebels. Given that weapons provided by the CIA to such groups ended up in Isis’s hands, this is surely naive. What needs far more scrutiny is the role of western allies such as Qatar and Saudi Arabia – which is armed to the teeth by Britain and the US, and whose social norms are all but identical to those of Isis.

According to the veteran Middle Eastern correspondent, Patrick Cockburn, Saudi Arabia and the Gulf monarchies are the “foster parents” of Isis. And the former head of MI6, Sir Richard Dearlove, has pointed out that Saudi financial support has proved critical to the rise of Isis. How long can western public opinion tolerate support for the Saudi dictatorship?

Foley appears to have suffered a despicably barbaric death; it is a fate being inflicted on many others. Because Isis has proved so successful in spreading terror, it will be difficult to have a rational debate about how to defeat it. But a rational debate is exactly what we need.