Steve Negus pulls out his map:

There seem to be two main fronts in the war right now -- one around Ajdabiya, the gateway to Benghazi and the east, and one around Misrata, Libya's third-largest city, with over half a million people. From a humanitarian standpoint, the situation around Misrata is much more critical. The city has been under siege for weeks, and power and water have been cut off. Pro-rebel websites are reporting via phone conversations with residents that Qaddafi forces are attacking the city, despite having declared a ceasefire. The regime may be trying to grab Misrata as quickly as it can and make its control of western Libya a fait accompli.

Rebel-held towns have in the past proven very difficult for the regime's armed forces to subdue, so Misrata may be able to hold out for days or even weeks. However, resistance in towns has also collapsed without much warning, so Misrata might be on the verge of falling. Either way, the civilian population is probably suffering very badly. This would be a situation in which the UN coalition would want to invoke the "all necessary measures" bit". While it's my understanding that it's fairly easy to spot and destroy tanks and artillery in the open desert, destroying vehicles in built-up environments would usually require going in low with close support aircraft, and that would be something that most air forces would be loathe to do without first spending a week softening up Qaddafi's anti-air defenses.

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