If Baghdad Falls-What Would Draw the US Further Into The War?

On 17 June 2015,the outgoing Chairman of the Joint Chiefs of Staff,General Martin Dempsey,US Army,and Secretary of Defense Ashton Carter testified before the House Armed Services Committee about the War On ISIL,with frank discussion of what circumstances would possibly increase US involvement.GEN Dempsey outlined the context of the conflict with the Islamic State in Iraq and the Levant by noting that:
1.Several governments in the region are struggling for political legitimacy.
2.There is a rivalry between Sunni and Shia Muslims.
3.There is rising competition between radical and moderate Islam.This will continually challenge the region's security forces.
We have an appropriate level of effort.This is an Iraq first strategy,but not an Iraq only one.We are at the beginning of a complex,non-linear campaign.We are constantly evaluating our approach and making sure we are resourcing it appropriately.
This has to be them winning.In our military campaign,we are on the path to delivering that which we are committed to providing:the ability to defeat ISIL on their sovereign territory.We're trying to build a network that will enable the region's players to confront this threat.
Why are we not targeting known ISIL assets?Leadership targets,fuel targets are authorised.We do strike those targets.The limitation is to try to avoid civilian casualties.Commander CENTCOM has the authority to select targets.Consider that 397 strike aircraft and 1650 pilots fly these missions every day.In my judgement,the avoidance of civilian casualties is not the limiting factor of our success against ISIL.
I think our strategy matches the complexity of what we're dealing with.The reality is,some of our Sunni partners are more worried about Iran's influence than they are about ISIL.We're reaching out to Sunnis at the request of Iraqi Prime Minister Abadi.
We've got almost 50% of intelligence,search and rescue unmanned assigned to Iraq/Syria.We of course are looking at points discrete where we might be providing additional resources to the Iraqi Security Forces where it would be strategically significant.Potentially,for example,an assault on Mosul,but I would be hesitant to make that permanent because we want them to do it independently.
If Iraq fails,added Secretary of Defense Ashton Carter,we will still try to enable local ground forces if they are willing to partner with us,but there wouldn't be a unified state.If Baghdad falls-I don't see that particular scenario as very likely,because Prime Minister Abadi has surrounded Baghdad with what remains,and the fact that they are Shia will make them fight fiercely.
What would make us more kinetic?asked GEN Dempsey:
1.A credible threat to the homeland.
2.A credible threat to our forces.
For example,I believe another 9-11 probably would draw us in.
Could we go in there and do a better job against ISIL?Absolutely,but we'd be back there two years from now.I would not recommend that we put US forces in harm's way simply to stiffen the spine of Iraqi Security Forces.If the threat from ISIL doesn't stiffen them,we won't,either.If the ISF go on the offensive with a strategic target,I would certainly go to the Secretary of Defense and have that conversation of how to increase their effectiveness,but not just to stiffen their spines,GEN Dempsey told the House Armed Services Committee.