The latest policy of intervention in Iraq and Syria, in particular, by the US, Britain, France and several Arab allies is problematic for many reasons:
Islamic State developed as a result of historic US backing for anti-Assad forces in Syria that have been funded and armed but have got out of control. IS has been known to US security forces for more than a year, but they generally turned a blind eye as long as IS opposed Assad, especially since Congress refused to support direct US intervention in the summer of 2013.
·Now IS has turned its attention to a larger project - a so-called Caliphate - and threatens US-backed Iraq and other status quo powers in the Middle East, including Saudi Arabia (who with Qatar have been backing extreme Islamists for decades, including al Qaeda. The US hoped that IS would help overthrow the Assad regime after which IS could be isolated and defeated or otherwise contained. This was pretty much the hope in Libya in 2011 (though with disastrous results as we can still see in what is effectively a failed state since violent regime change was instituted by the Obama adminstration and its allies).
There are pro-democracy groups in Syria that oppose Assad and IS but who have been generally neglected by the US. Those groups do not want US air strikes as they know who will suffer most. Such groups, including various Kurdish parties and organisations, have been sidelined because they contain a variety of views of the Assad regime and of foreign military intervention, as well as groups that desire a negotiated settlement, as opposed to ISIS' policy of all out war. The larger American project appears to be the overthrow of the Assad regime as is indicated by recent calls for a 'no'fly' zone over Syria - this is hardly a problem for ISIS as it has no airforce. It is a move against the Syrian airforce that would take the war directly to the Damascus government.
Hence the current intervention is a result of past interventions and machinations by the US and West and Arab allies more generally. The current air strikes are unlikely to achieve very much other than lead to many civilian casualties among ordinary Syrians and strengthen recruitment for IS.