It’s a bit beyond my expertise, but one thought comes to mind when I hear Iraq compared to Vietnam or other “quagmires”. When the Soviet Union got bogged down in Afghanistan, the Unites States was arming the mujahidin. Similarly, in the Korean War, the Soviet Union and China were arming the North Koreans. And in the Vietnam War, the same parties provided arms to the North Vietnamese. Even back in World War II, the heroics of the Warsaw partisans were backed by British ordnance.
This all raises one question: who will arm the Iraqi resistance? Ideally, stability will occur before those hostile to the U.S. occupation run out of RPGs and bullets. But failing that, and unlike in previous conflicts, it seems that there is a real chance that the opposition could run out of supplies. Despite U.S. belligerency, I don’t view it as likely that Iran or Syria will supply arms to Iraq (individuals could probably carry small arms over the border, but I doubt either government would participate). Turkey? Jordan? Saudi Arabia? Jordan? Kuwait? Those seem even less likely.