The fighting in Lebanon began abruptly and unexpectedly with Hezbollah’s cross-border raid on an Israeli patrol.It will not easily or abruptly be halted despite Israeli and Lebanese acceptance of the Security Council resolution on a “cessation of hostilities”.

The problems even in bringing about a ceasefire can be summarised as follows. The Lebanese Government desperately needs a complete end to fighting, but it cannot control Hezbollah. Israel will accept an end to fighting, but only if Hezbollah can be brought under control. Sheikh Hassan Nasrallah, the leader of Hezbollah’s military wing, does not want to stop a war that, he believes, recruits more extremists to the cause with every Israeli bomb dropped. He says he will abide by the ceasefire but also that he will attack Israeli forces so long as they are on Lebanese soil. This may well mean continued fighting, since Israel will not withdraw — and is not obliged by the UN to — until the Lebanese military and the reinforced UN contingent led by France are deployed from the Litani river to the frontier.

Since that deployment could take weeks, the clause in the resolution that allows Israel to respond to Hezbollah attacks simply recognises the political and military facts on the ground. In the short term, the best that can be hoped for is that fighting will gradually be contained to relatively localised skirmishes in Hezbollah strongholds, sparing the rest of Lebanon.

Still more severe tests will come with the movement to southern Lebanon of some 15,000 Lebanese troops, joined by an equal number of Unifil forces. Their joint task, according to the UN resolution, is to clear Hezbollah’s strongholds south of the Litani of all armed personnel, weapons and other military assets. More broadly, they are to implement previous UN resolutions calling for the reassertion of Lebanese sovereignty throughout the country through the disarmament of all armed groups, the removal of all “foreign forces” and an embargo on all supplies of arms to Lebanon “except as authorised by its Government”.

That may sound admirably clear; in the contorted politics of Lebanon, it is not. Its enfeebled Government, which contains Hezbollah ministers and politicians in league with it, might decide to “authorise” Hezbollah’s continued military existence, perhaps by bringing its fighters into the Lebanese Army. Kofi Annan, the UN Secretary-General, has unwisely hinted that “incorporation” might be a way out. The UN resolution relies heavily on the assertion of Lebanese sovereignty; but that seems little more than a legal fiction.

There will be no real chance of peace, therefore, unless Unifil disarms Hezbollah. The resolution authorises the UN force “to take all necessary action” and to resist armed efforts to prevent it discharging its duties, but — a curious caveat — only “as it deems within its capabilities”. France now says that these capabilities exclude disarming Hezbollah; Australia, sensibly, sees no point in committing troops if that is not to be part of their job.

France has manoeuvred skilfully so far; it must now, as its diplomats say, follow the “logic of events”. UN military observers watched but did not act or speak out as, after Israel’s withdrawal from Lebanon six years ago, Hezbollah trained, strengthened its bases and imported its huge arsenal of rockets. It falls to France to ensure that the tragedies of recent weeks will not, on the UN’s watch, be repeated.