What does Gaddafi's ceasefire offer mean?
If sincere, the ceasefire offer could mean an end to the violence, potentially opening the way to negotiations with the opposition, possibly under United Nations auspices. But it's a big "if".
Libyan leader Muammar Gaddafi is a master of propaganda and disinformation. To accept the offer, western and Arab countries would have to be convinced that the regime's forces had genuinely laid down their arms across the entire country; the ceasefire would have to be independently verified; and they would have to be convinced it was permanent.
That said, a ceasefire at this stage could also cause serious political headaches. It would leave Gaddafi in power, although his situation would be much reduced and that would fiercely complicate efforts to create a new system of governance in the country. Without genuine reform, instability and violence would return sooner or later.
Could Libya be split in two?
If Gaddafi survives this crisis, maintaining his grip on the capital Tripoli and most of western and southern Libya, and if the opposition remains centred on Benghazi in the east, and if there is no agreement between them on reform but rather an uneasy or frozen peace, it is entirely possible that Libya could split in half.
Such a development would reflect historic cultural and tribal differences between east and west. And there are plenty of precedents for partition following or preceding conflict: the US split between Union forces and Confederates, the two Koreas, the two Germanys, Kosovo and Serbia, and north and south Sudan to name a few.
Quite how two separate Libyas might function economically, and how energy wealth would be divided up, are complete unknowns at this point.
What did the UN resolution permit the participating allies to attack?
The security council vote gave wide-ranging authorisation for the use of force against targets in the air and on the ground, according to most international lawyers. The phrase in paragraph four of resolution 1973 calls on member states "to take all necessary measures … to protect civilians and civilian populated areas under threat of attack …"
Malcolm Shaw, professor of international law at Leicester University, described it as giving the broadest powers for intervention since the UN resolution deploring the Iraqi invasion of Kuwait in 1990.
Airfields, air defences, artillery and supply convoys could also be attacked, if they are clear and identifiable targets. "This would involve bombing Libyan airfields and air defences," said Richard Piotrowicz, professor of international law at Aberystwyth University. "It does not mean they only attack aircraft in the air. However, it would not justify French or British aircraft destroying Libyan forces just for the sake of it."
Declaring a ceasefire does not invalidate the UN's no-fly zone. "There's no condition saying the resolution will stop because of [any] action by the Libyan authorities," Piotrowicz said.
Gaddafi is likely to be held accountable for attacks on rebels carried out by gunmen or partisans. It may well be argued that he has allowed his forces to get out of control and could have prevented such violence.
What is the state of Gaddafi's forces?
The Libyan air force may have as few as 40 operational fixed-wing aircraft, mainly ageing Soviet-era fighters, although there are a small number of more modern French Mirage F1s.
"The Libyan air force is very weak and could easily be taken out," said Shashank Joshi, of the Royal United Services Institute. "Their aircraft are old and poorly serviced and they are flown by poorly trained and demoralised pilots. Their pilots are unlikely to want to fly what may be regarded as suicide missions."
What military hardware will Britain provide?
Tornado and possibly Eurofighter-Typhoon ground attack aircraft, Awacs long-range early-warning aircraft, the frigates Westminster and Cumberland, Nimrod R1 reconnaissance aircraft, refuelling tanker aircraft and possibly Chinook helicopters to transport special forces.
Why did the US drop its opposition to armed intervention?
The last few weeks saw an intense debate within US president Barack Obama's administration over the wisdom of getting involved. But several key factors seem to have swung the argument in favour of intervention.
One was the realisation that Obama, who made reform and democratisation in the Arab world a key plank of his foreign policy when he spoke in Cairo in 2009, could not stand by and watch as Gaddafi crushed the uprising.
Another was analysis suggesting that if Gaddafi survived the revolt he would revert to his old anti-western, terrorism-sponsoring ways and become a real threat to US interests.
The fact that the Arabs themselves were calling for intervention, and were prepared to send forces to implement it, also helped change Obama's mind. Tellingly, once he decided to act, he expanded the scope and scale of the action, just as he did when he ordered the 2009-10 troop surge in Afghanistan.
Is the UN vote – and Gaddafi's ceasefire announcement – a personal triumph for David Cameron?
Cameron surprised many observers by his tough stand on Libya, given his previous narrow focus on domestic policy and foreign trade. Cameron, relatively inexperienced in foreign policy, seems to have been genuinely appalled by Gaddafi's attacks on his own people – and he appeared to have scant confidence that the EU could stop him.
But Cameron was also extremely critical of Labour's too-cosy relationship with Libya during the Blair-Brown years, which led to the extradition of the Lockerbie bomber and a big row with the US. He was determined to act differently.
Forming an alliance with France on the issue of a no-fly zone was the natural thing to do, given that Britain and France are Europe's only significant military powers. The two countries then used their joint leverage to push for American support.
The fact that Obama was eventually won over made the UN vote possible. So those who believe intervention is the right thing to do will feel this outcome represents a significant political victory for the British prime minister. If the intervention goes wrong, Cameron will, of course, be personally blamed, as was Blair over Iraq.
Why did Germany refuse to support the UN resolution?
Germany opposed military intervention every step of the way, as it did in Iraq in 2003, and it abstained in Thursday's UN vote.
But, unlike Iraq, this intervention is now sanctioned under international law and is supported in the region. Angela Merkel, the German chancellor, argued a "civil war in north Africa" had nothing to do with Germany and Europe. That seemed shortsighted, given Libya's proximity. Critics say Merkel was worried about approaching elections and overly influenced by the unpopularity of Germany's involvement in Afghanistan.
Germany's opposition to intervention is potentially very damaging to Berlin's already strained ties with other major European countries, to the cohesion of the EU, and to the credibility of Nato.
Was the resolution a victory for Nicolas Sarkozy?
Sarkozy faces an uphill presidential re-election battle next year. His approval ratings are low, the economy is suffering, unemployment is high, his personal style is criticised and he recently faced a rebellion by France's diplomatic corps.
His government's misjudgment of January's Tunisian revolt, when France appeared to support the regime against the pro-democracy protesters, was embarrassing, especially given that France is supposed to have unique insight into north Africa, where it was once the colonial power.
But Sarkozy's success in championing the Libyan intervention, his early recognition of the Libyan rebel "government", and his apparent determination that French planes lead the assault could be crucial in turning things around for him politically.