As the US prepares to send 450 more troops to Iraq to help train security forces there to fight against the Islamic State, some argue that this number is simply not enough.​

Calls for upwards of 10,000 US troops to be sent back to Iraq are now coming from lawmakers and heavy weight think tank analysts.

​But advocates for the war in Iraq have tended to want to get into the weeds before asking some of the more fundamental questions – including whether more US trainers would actually improve the situation on the ground. Is there a point, for example, at which US troops can salute smartly and declare "mission accomplished," serene in having achieved a clear goal that allows them to no longer feel responsible for what happens after they leave?

Here are six of the big questions the Pentagon is grappling with, even as calls for more troops to the region continue: