Nearly nine weeks after Bashar al-Assad's regime formally agreed the UN six-point peace plan, and six weeks after the ceasefire was supposed to come into effect, the killing continues unabated.

No one should be surprised. For this regime, the Kofi Annan plan was never more than a fig leaf for its continued attempts to bludgeon the opposition into submission. Damascus knows that Russia and China will continue to veto any meaningful action by the Security Council. Assad can count on the loyalty of key military and intelligence units dominated by his Alawite sect. Regionally, he enjoys the unwavering support of Iran and the tacit support of neighbouring Iraq and Lebanon. International sanctions have had an impact, but will not by themselves bring down this regime.

Crucially, the Syrian dictator calculates – correctly – that the West has little appetite for direct military intervention. Harsh words are all he has to fear from the likes of Barack Obama or William Hague.

This is a regime that has always ruled by terror. With the world sitting on its hands and with key global and regional states onside, it has had no reason to alter its strategy. It has been careful, however, not to kill on a scale that might shift the global balance. It appears to have calibrated its violence carefully. Usually, it guns down or cuts the throats of "only" 30 or 40 people per day.

That may change. Saudi Arabia and Qatar are now supporting the rebels with more than empty words. The new equipment reaching the Free Syrian Army is likely to include weaponry effective against armoured vehicles.

If the regime is no longer able to use its armour at will, it may have to rely increasingly on long-range artillery and air attack – with horrendous implications for casualties. In turn, this could swing international public opinion decisively against the regime, making serious intervention more likely.

The conflict looks certain to be long and bloody. The longer it continues, the more chance of extremist Islamist involvement, the greater the danger that it will spill over into neighbouring states, and the greater the risk of sectarian war, Syria being a patchwork of antagonistic religious and ethnic communities.

The world worries that intervening might make matters worse. But serious intervention could decisively shorten the war – and thus minimise the very risks that the world most fears.

Alan George is a senior associate member of St Antony's College, Oxford. He is the author of 'Syria: Neither Bread Nor Freedom'