An old saying stressing the importance of the supply and maintenance aspects in any military operation, and the reason why those who engage in direct battle operations are a small percentage of the total military strength in Iraq.
I learned all this from science fiction or fantasy, by the way. Elizabeth Moon's The Deed of Paksenarrion, probably. Just to explain why a female divine would say anything about this stern and manly bidness of war.
Now the hook, as they call it in writing, meaning the reasoning for my babble above:
A point seemingly missed in much early coverage of the UK withdrawal from the south (that I have seen, at least) is the potential impact of that withdrawal on the eventual withdrawal of US forces.
There already has been discussion of how vital the Baghdad-Kuwait supply line is for ongoing US operations, and this concern is well-founded. The south is not as has been portrayed in some upbeat UK and US official comments today. Southern Iraq is a very much troubled region where most localities are dominated by militias (sometimes rival militias), governance (to the extent governance linked to Baghdad exists at all beyond the symbolic in large areas) is tenuous, security forces are in most cases far more loyal to militias (often local, semi-autonomous militia elements) than legal authorities (such as the mayor of Basrah), criminality (including large-scale oil & fuel smuggling) is endemic, and low-level assassinations of the relatively few Sunni Arabs still present there is ongoing.
My bolds. Now I'm feeling hungry, again.