A strong Assad means Syria will continue to play a pivotal role in maintaining a military front opposed to Israeli hegemony in the Middle East. That in turn means a strong Iran and a strong Hizbullah, the Shia militia in Lebanon.
Hizbullah's formidable record in guerrilla warfare is the main reason Israel no longer occupies south Lebanon. Similarly, Hizbullah's arsenal of rockets is a genuine restraint on greater Israeli aggression towards not only Lebanon but Syria and Iran too.
Israel's air strikes in early May appear to have targeted shipments through Syria of more sophisticated weaponry for Hizbullah, probably supplied by Iran. Longer range missiles and anti-aircraft systems are seen as "game-changing" by Israel precisely because they would further limit its room for offensive manoeuvres.
Israel will be equally stymied if Assad stays in power and upgrades his anti-aircraft defences with the S-300 system promised by Russia.
Either way, Israel's much vaunted ambition to engineer an attack on Iran to prevent what it claims is Tehran's goal of developing a nuclear bomb -- joining Israel in the club of Middle Eastern nuclear-armed states -- would probably come at too high a price to be feasible.
So what does Israel consider in its interests if neither Assad's survival nor his removal is appealing?
According to some well-placed Israeli commentators, the best Israel can hope for is that Assad holds on but only just. That would keep the regime in place, or boxed into its heartland, but sapped of the energy to concern itself with anything other than immediate matters of survival. It would be unable to offer help to Hizbullah, isolating the militia in Lebanon and cutting off its supply line to Iran.
In closed-door discussions, analyst Ben Caspit has noted, the Israeli army has put forward as its "optimal scenario" Syria breaking up into three separate states, with Assad confined to an Alawite canton in Damascus and along the coast.
A long war of attrition between Assad and the opposition has additional benefits for Israel following the decision by Hizbullah's leader, Hassan Nasrallah, to draft thousands of fighters to assist the Syrian army. Protracted losses could deplete Hizbullah's ranks and morale, while fighting is likely to spill over from Syria into Lebanon, tying up the militia on multiple fronts.
But there is a risk here too. If Hizbullah performs well, as it did in defeating the rebels this month at the town of Qusayr, its position in Lebanon could be strengthened rather than weakened. And in that situation Assad's debt to Hizbullah would only deepen.
Such calculations are doubtless exercising Israeli military minds.
The greatest danger of all is that yet more parties get drawn in, turning the conflict into a regional one. That would be the likely outcome if Israel chooses to increase its interference, or if the US comes good with its recent threats to increase military aid to the opposition or impose a no-fly zone over parts or all of Syria.
Either way, Israel might see the transformation of Syria into a new mini-cold war theatre as advantageous.
However, the Israeli sphinx isn't offering any answers quite yet.
A version of this article first appeared in The National, Abu Dhabi.
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