Very good Open Democracy piece by Tim Garden, who was formerly Assistant Chief of the Uk Defence Staff. Sample:

Four distinct groups now threaten Iraq. First, former regime elements, who are largely drawn from the Sunni population, and number somewhere between 15,000 and 30,000 fighters. There are then two different groups of Islamic extremists who can field suicide attacks. The foreign fighters, including those led by Musab al-Zarqawi, number about 1,000. A new development is the emergence of home-grown Islamist insurgents. They are still fewer than 500, but their numbers are increasing and they can deliver great destruction. Fourth, the biggest security problem of all comes from organised crime. At least twelve of Iraq’s eighteen governorates have a major crime problem, particularly when the criminals work with the insurgents.

Garden sees two possible outcomes:

1. A fragile, but improving, situation in Iraq with the hope that coalition forces might leave by the end of 2006.

2. A country which begins to look more like Afghanistan than Vietnam, with increasingly lawless regions. The prospect for coalition forces is then without limit, as the worst route of all would be to abandon Iraq and allow it to become a force for instability in the region.