This week the civil war in Syria revealed its full potential for destabilising the Middle East as a whole. After the Israeli air strikes, Hezbollah acknowledged its forces were fighting alongside those of Syria's president Bashar al-Assad and suggested Syria would respond by fully arming Hezbollah fighters.
With Hezbollah engaged in securing Assad's corridor to the sea, and with the tensions between the Shia-dominated government of Nouri al-Maliki and demonstrators in the Sunni provinces at its height in Iraq, it is not difficult to wargame a conflict that freewheels over three countries – Iraq, Syria and Lebanon. A war that has already killed 70,000 Syrians, displaced 4 million and forced 1 million to flee could get a lot worse.
That is why it is right for Barack Obama to resist pressure from Britain and France to arm the rebels, and to instead make another attempt at an internationally brokered settlement with the Russians.
With the Free Syrian Army losing ground and possibly also cohesion – whole units are defecting to the better-armed Jabhat al-Nusra, an Islamist organisation with links to al-Qaida – it is clear that managed militarisation by drip-feeding weapons to change the balance of power is not working.
Assad may have lost control of much of the country, but his army has kept its cohesion, it has huge destructive power in reserve, and there is nothing to indicate he will still not be around in a year's time.
That realisation leaves all the countries backing the rebel factions with broadly two options, neither of them easy. As a forthcoming report by the European Council on Foreign Relations (ECFR) argues, the current fallacy is that there is a choice between two painless options – a military lite and a diplomacy lite course of action.
The former assumes rebel fighters that the west is in a position to handpick (the French foreign minister, Laurent Fabius, is pressing the UN to declare Jabhat al-Nusra a terrorist organisation). The latter assumes diplomacy in which Assad will eventually agree to step down.
The reality is that the international community faces two harder and uglier choices: full militarisation – establishing no-fly zones, arming the opposition with the heavy weapons they need; or, as the ECFR report persuasively argues, de-escalation.
With massacres happening regularly, matching Assad's firepower with an equivalent one appears to be the moral thing to do. It would provide a short-term answer to those who say another Bosnia is unfolding before our eyes.
But in the medium or longer term, refuelling this conflict looks less attractive. It would be more than a replay of Iraq. It would dramatically increase the daily death toll. It would oblige Iran and Russia to arm Assad with heavier weapons.
Why would Assad, Iran and Hezbollah back down in what would become an existential struggle? And what exactly would that victory look like now? A Syria liberated of Assad would still leave an armed Alawite minority in fear of its lives. The civil war could well outlast his fall. Victory would also reveal the fault lines in the rival rebel groups claiming it. Post-Assad Syria could be Libya writ large.
This leaves the second alternative: de-escalation. This is a lengthy series of compromises, which would be portrayed inside Syria as a sell-out. It means pressuring the Gulf states to starve rival militias of arms. Without that happening, there is no political solution.
It means the leaders of Syrians whose families are being cut to pieces by Assad's weapons accepting that he remains part of the transition. It took only 24 hours for this crack in John Kerry's deal with Sergei Lavrov to show through. For Russia and Iran to cut their military support, Assad's fate has to be a product of the transition, not a precondition of it.
Only by starving this fire of all of its external supplies of oxygen will the incentives to come to the table increase. This requires sustained pressure – from all sides.