The first terrorist attack in Tehran in more than a decade underlines how the shifting dynamics of the Syrian conflict are being felt far from the battlefield. In separate incidents in the Iranian capital on Wednesday, suicide bombers and gunmen struck at the heart of the country’s religious and political establishment by targeting the mausoleom of the Islamic Republic’s founder, Ayatollah Ruhollah Khomeini, and the national parliament. At least 12 people were killed and dozens of others wounded.
If the Islamic State's claim of responsibility for the terrible attacks is borne out, it will be the group's first successful assault on Iran, whose support for the Syrian government and pro-regime militias has made it a key player in the Syrian civil war.
But while the attacks will unsettle Iran, not least as they come at a time of acute tension between Tehran and its Sunni rival, Saudi Arabia, the Iranian leadership will nonetheless be aware that Islamic State is taking its fight farther afield partly because it is in on the back foot in its self-proclaimed caliphate in Syria and Iraq.
In the past year the territory under Islamic State's control has contracted dramatically, and its fighters are coming under intense pressure in some of their remaining strongholds. Pitched battles are under way in Mosul, where Iranian-backed militias and US warplanes are assisting the Iraqi military in what appear to be the final stages of a long battle to retake control of the city. After months of advances in northern Syria, the US-backed Syrian Democratic Forces, which includes Arab and Kurdish militias, announced on Tuesday that it had begun an operation to capture Raqqa, Islamic State's de facto Syrian capital.
Western authorities have long warned that the more ISIS finds itself in retreat in Syria and Iraq, the more likely it is to seek to distract from its losses and boost morale among its followers by staging attacks elsewhere. Attacks such as those in Manchester and Tehran can be seen in that light: as a sign of Islamic State weakness, not strength.