Viewpoints: How to defeat the Islamic State group
The militant movement Islamic State (IS) has taken advantage of political chaos in Iraq to launch a brazen offensive.
The group was already in control of many areas of Syria, and its advance in Iraq has seen it take large swathes of the north of the country, including the city of Mosul.
Shortly after seizing Iraq's second city, IS declared the creation of a caliphate, or Islamic state, in the territory it controls.
Five leading analysts give their views on how IS can be stopped.
'Islamic State is likely to be a threat for years'
Islamic State can be damaged by airstrikes, but it will only be defeated if its Sunni allies turn against it and responsible governance redevelops on both sides of the Syrian/Iraqi border.
Iraqi Prime Minister Nouri Maliki's removal is far from a panacea - for one, it only addresses the Iraqi side of the border - but it is the first step in what would be a long and perilous process of establishing a government in Baghdad capable of accommodation with all elements of the Iraqi population.
Frankly, I'm sceptical that Mr Maliki's successors will either want or be able to achieve that goal, but that is a risk that must be accepted.
Islamic State benefits from war and the fear it breeds - and the strategy to counter it must focus on bolstering stability: blunt Islamic State's advance; support states like Jordan on the Islamic State's periphery; help the Kurds defend themselves; support Sunni factions irreconcilably opposed to Islamic State; and try to bolster the Shia-led government in Baghdad without empowering Iranian-backed extremists.
This is a tall order and it is not likely to defeat Islamic State any time soon. But it is the strategy that should be pursued, with eyes wide open that some version of Islamic State is likely to be a threat for years.
Brian Fishman - New America Foundation
'Iran and the US share a common objective'
Three main objectives need to be achieved to decisively defeat Islamic State: strengthening state institutions - including armies - eliminating the group's freedom of movement, and co-opting its local and regional backers. The United States and Iran differ on a lot of things, but when it comes to IS, they clearly share a common objective.
Iran can facilitate military and intelligence cooperation between the Iraqi and Syrian governments.
If IS is only confronted in Iraq, it will retreat to Syria to come back another day. Tehran is also capable of ensuring that Shia militias won't go rogue and eclipse IS as a security threat.
There are many obstacles to overt, direct military and intelligence cooperation between Iran and the US at this point.
But if the Iraqi authorities play their cards right, they can once again act as a conduit for Iranian-American dialogue. Being a bridge instead of a battleground between Iran and America would greatly benefit Iraq.
If Baghdad and Irbil can pool military, intelligence and political assistance from Washington and Tehran, the efficacy of efforts to target IS as well as undermine both local and regional support for the group would be substantially improved.
Mohammad Ali Shabani - Iranian political analyst
'Confronting IS needs a regional strategy'
This week's political changes in Baghdad will be more important than US air strikes in determining the fate of IS.
Haider al-Abadi has a honeymoon period in which he will benefit simply from not being Nouri al-Maliki. His ability to forge a basic political consensus with rival Shia, Sunni and Kurdish factions, against the common threat of IS, is vital to the future of the state.
In 2007-08 it was mainly Sunni militias that defeated IS's precursor, al-Qaeda in Iraq. Despite this, Sunnis have been disproportionately targeted as potential terrorists by Mr Maliki's government. Although IS's intolerant ideology is not popular, the Baghdad government is also hated.
Civilian deaths from air strikes - with the Iraqi air force reportedly firing barrel bombs into residential areas - will hardly help. Nor does the fact Baghdad has military help from Iran, which is helping President Bashar al-Assad violently repress what was initially a peaceful uprising in Sunni-majority Syria.
Confronting IS will also need a regional strategy to tackle its funding and recruitment, and above all to solve the conflict in Syria, where many of its fighters have been radicalised.
As IS condemns both the Saudi and Iranian regimes, could the two rival regional powers see some common interest in helping make peace in Syria, and helping Mr Abadi fight it?
Jane Kinninmont- Chatham House
'Britain could ease the burden on US forces'
Britain has a number of interests at stake in Iraq. Over 500 Britons have travelled to the region to fight alongside Islamic State and associated jihadist groups, Britain is closely allied to vulnerable neighbouring states like Jordan, and it was British jets that enforced the 12-year no-fly zone that sheltered Kurds after the Gulf War.
The UK has therefore watched the group's rise with concern, but ministers are wary of an open-ended military commitment the year before national elections.
Although the UK has only conducted airdrops of food and water thus far, the Tornado fighter jets it has deployed to Cyprus would allow it to quickly ramp up operations.
It could also contribute refuelling, reconnaissance, and transport aircraft, as well as deploying its special forces, who have extensive experience of Iraq, to gather intelligence and guide air strikes. Britain could thereby ease the burden on US forces.
But these UK forces are only likely to be used for a short mission, and in line with US objectives - defending Kurdish territories and relieving trapped minorities, not defeating IS.
To degrade Islamic State over the longer-term, the UK should focus on arming, training, and indirectly supporting Kurdish forces, and helping Haider al-Abadi's new government to rebuild his country's shattered army.
Shashank Joshi - Royal United Services Institute
'New government must reach out to Sunnis and Kurds'
The key to defeating Islamic State is not military, but political.
It is the ability of the new government to reach out to the Sunnis and Kurds, make it clear that the slide towards sectarian division is over, show that nation's political power and oil wealth will be shared, and demonstrate that it is returning to the creation of national Iraqi security forces rather than Shiite forces and militias.
The US can only help, and only succeed, if Iraqis are willing to unify enough to be able to help themselves. Even then the prospects of success are uncertain.
Nouri al-Maliki pushed the nation towards division and civil war too long, defeating IS will not be easy, and even its defeat or collapse may leave Iraq too divided.
Anthony Cordesman - Center for Strategic and International Studies