As events unfold in Baghdad, President Obama's decision to unilaterally withdraw US troops from Iraq in the absence of a Status of Forces Agreement appears vindicated. Prime Minister Maliki has exacerbated the sectarian nature of Iraq's politics, bringing the current crisis to a head. The White House must be thanking its lucky stars that it doesn't have troops working for a prime minister who is refusing all entreaties to leave.

Some commentators have opined that ISIS would not have had its successes in Iraq had there been a residual US troop presence. The reality is that ISIS has assiduously courted the Sunni tribes disenfranchised by Maliki's government, and the Iraqi military has become hollow and corrupt. A small residual US force would have been at best spectators to, and at worst complicit in, Maliki's mismanagement of the situation. Greg Sheridan's view in The Australian that 'a residual (US) force would have helped stabilise Iraqi politics and bolster the Iraqi military' is typical of the 'if only' brigade – it ignores the complex reality of Iraq's secular, religious and tribal dynamics.

That is why in some ways ISIS's decision to launch attacks against religious minorities and the Kurdish region has presented President Obama with a strategic gift which he has been quick to act upon. Iraq clearly needed military assistance but the US needed to offer it in such a way that it wouldn't be seen to profit Maliki politically. What better way to introduce US firepower than in support of a humanitarian cause and in defence of Kurdish-controlled areas? It came with the imprimatur of the Iraqi Government but is not directly in support of it. It is a difficult act to juggle but it gives the US some leverage: if Maliki tries to cling to power, expect a narrow range of US military support. If he leaves and is replaced by a more inclusive government, then air support could be more widely employed.

For its part, ISIS is beginning to learn the difficulty of trying to fight a conventional military campaign using captured equipment when your enemy has air supremacy. As far as we know, US airstrikes have only destroyed an artillery piece, a mortar baseplate, some armoured vehicles and a vehicle convoy, but even the rabid ideologues of ISIS will start to sense that trying to manoeuvre in the open plains of northern Iraq is fraught with danger when US strike aircraft lurk overhead. Nor will the demonstration effect of a few 500lb bombs and Hellfire missiles have been lost on the other protagonists. Iraqi and Kurdish forces are likely to fight more vigorously if they know air support is at hand. Moreover, should US air support be broadened in support of a more inclusive Iraqi government, Iraqi tribes now aligned with ISIS may decide that their interests are better served by opting out of the Islamist coalition.

These are all big ifs, and the situation in Baghdad is unfolding hour by hour. But it may well be that ISIS's decision to press ahead with attacks against minorities and the Kurds is a strategic, rather than just tactical, error.

Photo from Flickr user United States Forces Iraq.