'go to war'.
Semantics surely. Would you have preferred it if I'd written 'engage in military conflict', or 'deploy a military force capable of defeating IS in battle and returning the territories they have illegally taken by force back to he people they now brutally oppress'?
Look at the Middle East and North Africa. IS had made huge gains. My point stands, the earlier the intervention the more limited the conflict. The longer we wait the more protracted and bloody it will be.
Right now they are more able to win millions of young and not so young hearts and minds all around the world through their slick propaganda because they are winning. An emphatic military defeat is needed to undermine their credibility among those susceptible to their cause.
Anyway, I'm hardly an authority on military matters, but I know someone who is;
http://www.theguardian.com/world/2015/may/24/ex-army-chief-urges-pm-to-consider-boots-on-the-ground-to-fight-isis