What single factor could you remove that would cause that area to cease being a warzone?

The answer is ....... The Americans.

Ah Lox your bias is showing again

Besides go back and read what I actually said. I do not believe I have ever used the term warzone in any of my posts.

Greatest cause of civilian deaths in Iraq? Fellow muslim killing fellow muslim - Fact. Foreign Jihadists; Ba'athist insurgents; Sectarian Militias and criminal gangs all played their part, which you somehow seem to totally ignore. Saddam Hussein releasing every single criminal in the country immediately before the US forces invaded did little to help either, but there again as you no doubt will be able to tell us Saddam always had the best interests of Iraq and the Iraqi people at heart. Of course had Saddam been left in place and maintained his averages he would have continued to have killed somewhere between 154 and 282 Iraqi citizens every day, as he had done for the 24 years of his rule. Probably more as he would now be into the fourth year of Iraq's second war with Iran.