How does one know? What if the Sunni insurgency is about 200,000 and the Shii insurgency is about 200,000 - 400,000? What if the insurgency has popular support - as in support of several million Iraqis who want the US out of their country?
There is something like 138,000 US personnel in Iraq (http://www.globalsecurity.org/milita...iraq_orbat.htm
) with about 7200 UK personnel (http://news.bbc.co.uk/2/hi/uk_news/4094818.stm)
, and several thousand others from other countries (aka coalition forces).
Maybe the US, UK and coalition are outnumbered.
It is not the liberal thinking, but the poor planning and sloppy 'post-war' operations. Rumsfeld interferred and never allowed the generals to deploy adequate forces, and neither did the president who didn't command, at least not effectively.
Many in the military and intelligence communities concede that Bremer should not have summarily dismissed the Baath party members or original Iraqi army. A few million might have bought them off. Instead they were shutout and their only recourse was to go underground and the insurgency began - 72 hrs after Bremer executed CPA-2.
So, much of the current situation could have been avoided (maybe).