Historically, the east of Libya centred on Benghazi is quite distinct from the rest of the country and has suffered disproportionately under Col Gaddafi. It is not impossible that the country will be effectively divided while a civil war ensues. We have no mandate from the UN to intervene on the ground to help the anti-Gaddafi forces take Tripoli. We could, of course, arm them, which would allow them to defend the territory gained but we are then drifting further away from humanitarian intervention and closer to direct military involvement. More importantly, it might make it more difficult in future to secure Security Council backing for future humanitarian interventions.
From a parochial British point of view, we will want to gauge whether removing Col Gaddafi, as opposed to stopping his attacks on his own people, matters sufficiently to us as to be prepared to see our soldiers actively engaged on the ground. In reaching a decision are we motivated by a desire to protect our own security and energy supplies or are we inspired by the obvious wish of significant elements of the Libyan people to be free of the Gaddafi incubus? Almost certainly the latter.
But after the bitter experiences of Iraq and Afghanistan, public opinion will want to know what the exit strategy is. If we are prepared to intervene on the ground to save Benghazi from being overrun by Col Gaddafi, how long would we be prepared to remain?