How do you solve a problem like ISIS?

When huge swathes of Iraq were taken over by the militant jihadist group ISIS (the Islamic State of Iraq and al-Sham, also known simply as the Islamic State), the Iraqi government wasted no time in calling for foreign assistance. The weakness of the state – which is wracked by sectarian tension and political deadlock – was highlighted by the lack of defence put up by the Iraqi army. Yet despite the obvious dangers to the region and the world of an extremist group so brutal that even Al-Qaeda has disassociated itself, international military assistance has been somewhat slow.

ISIS recently declared a new caliphate in the land it controls across Iraq and Syria. Of course, this proto-state has not been recognized internationally, but this large area in which ISIS can operate with impunity has provided the group with a space from which to launch further attacks. It recently took land from the Kurds, whose Peshmerga fighters were previously seen as the only force in Iraq capable of resisting ISIS. The group now controls about a third of Iraq.

The news last week that tens of thousands of refugees were trapped on Mount Sinjar prompted western countries to step up their involvement. The US has been conducting airstrikes on ISIS targets in Iraq’s north, and carrying out airdrops of food and water to refugees. France said this week that it would arm the Kurds, who are also receiving US military aid. The UK has pledged to join a rescue mission for displaced civilians. An American scouting mission to Mount Sinjar this week found that fewer refugees than expected were there, leading the US and UK to call off a risky rescue mission. However, David Cameron said that both countries would retain a flexible military presence in northern Iraq.

The question of western intervention in Iraq is a highly charged one. Many analysts see the disastrous 2003 US-led invasion of the country as the root cause of the current crisis. Poor planning for what would happen after regime change was achieved resulted in a power vacuum, a weak state, and a worsening of sectarian tensions. Yet analysts and politicians alike are sharply divided on the best course of action now: does this partial responsibility for the current situation mean that the west has an obligation to step in, or has enough damage already been done?

Leaders in the UK, US, France, and Australia have all repeated the mantra that there will be no “boots on the ground” in Iraq. For a ground force to return to the country so soon after the long and unpopular war drew to a close would be politically difficult with populations both in Iraq and in the west. But, of course, it’s an abstract distinction. There are already about 1,000 American advisers in the region. There have been some calls – including from former defence secretary Liam Fox – for Britain to join America in a combat role.

The current western involvement in Iraq is very clearly justified on humanitarian grounds, to save the lives of thousands of fleeing refugees. Last week, the UN warned of an imminent genocide of the Yazidis. Yet analysts have warned of “mission creep”, which BBC security correspondent Frank Gardner defines as “a small, narrowly defined operation ballooning out of control, sucking in western countries into a lengthy conflict with no clear exit”. After the refugees are escorted to safety, the fundamental problem will still remain: that ISIS, an aggressive and extremist force, is in control of a substantial proportion of Iraq, and is capable of seizing more land in the region. It is easy to see circumstances in which western military intervention would be stepped up. If ISIS is able to threaten Baghdad, or the capital of Kurdistan, Erbil, then it would be difficult for the US to hold back. Airstrikes have so far, apparently, been highly effective; but that becomes complicated if the fighting moves to more densely populated urban areas, where civilian populations are at risk.

At present, the focus is on providing humanitarian aid and strengthening the Kurdish regional government and forces to better fight the threat. But some observers of Iraq suggest that it is just a matter of time before the US and UK combat role steps up; the short-term goal of rescuing refugees and securing Kurdistan are clearly defined, but the broader problems of ISIS and the instability of Iraq cannot feasibly be ignored by the international community, given the threat it poses not only to human life in Iraq, but to other countries in the region and the world. What form stepped up action takes and how long it will be before the goals in Iraq begin to shift remains to be seen; certainly, the threat of ISIS is not going to disappear.