The challenge of Libya can only get tougher

There is no turning back now. Britain has struck at Colonel Gaddafi's forces; the Libyan dictator has promised to fight a ''long war'', which we must pray is not the case – but, whatever the circumstances, our servicemen and women deserve our full support. Although it appears to have been French planes that first attacked Gaddafi's troops after the breaking of the ceasefire, the broad-ranging Western coalition would not have been assembled so quickly without the passionate diplomatic efforts of David Cameron. If Libya is liberated from its homicidal dictator without much bloodshed, and a peaceful regime takes his place, then the Prime Minister will deserve – and receive – enormous international credit.

That is, however, a big if. No sooner had the first missiles been fired than the Secretary General of the Arab League criticised the bombardments. According to Amr Moussa, the action exceeded the United Nations remit for a no-fly zone. ''What we want is the protection of civilians and not the bombardment of more civilians,'' he said. Indeed; but Col Gaddafi, deranged though he may appear, is easily clever enough to ensure that innocent Libyan civilians die as a result of allied action.

The instant wavering from the Arab League was sadly predictable; it is one of the reasons this newspaper urged the Western powers to make sure that, if they went down the route of a no-fly zone, it was policed by the substantial air forces of the leading Arab powers. In the event, it is by no means clear what sort of bombing raid, if any, the Arab League will support once pictures of casualties start appearing daily on al-Jazeera.

The challenge now for the Nato powers is to know how to respond to a possible groundswell of Arab opinion against their intervention in Libya. Will they stand united? The omens are not particularly good. President Barack Obama believes that the UN resolution does not authorise the use of ground troops; yet George Osborne and William Hague yesterday declined to rule it out.

It is all very well to say that the American and British governments want to topple Gaddafi; but if they have different ideas about how far they can go to achieve this aim, then British forces could find themselves shouldering too much of the burden – which is precisely why we urged caution before embarking on military intervention. In foreign affairs, as in so many areas, Mr Obama's intentions are hard to read; if he thinks the Libyan intervention will damage his standing in the Middle East – or the Midwest – then there is no guarantee that he will not make America's excuses and leave. Moreover, there is no evidence that either he or Mr Cameron has considered what sacrifices might be needed to remove Gaddafi, let alone a clear vision of what a post-Gaddafi Libya ought to look like. Despite the pressure of the military campaign, they must do that thinking right away.