Along with the Russian air intervention begun last September and the Iranian Revolutionary Guard, Hezbollah’s fighters have enabled Assad to make progress against his opponents, especially those associated with the Free Syrian Army fighters backed by the United States. That progress has hardened Assad’s negotiating stance and blocked the UN search for a political solution.
A shift in the military balance is essential to ending the war, which is what Washington says it wants. But 44 has steadfastly refused to go to war against the Syrian, Iranian or Russian government.
But Hezbollah is a non-state actor.
It’s also a US-designated terrorist group that has murdered Americans, among many others. Most Republicans and Democrats would applaud an attack on Hezbollah, even if some in both parties would bemoan a move that suggested widening commitments overseas.
Washington could inform Tehran, Moscow and Beirut that Hezbollah should withdraw from Syria by a certain date or the United States would target any of its troops attacking non-extremist opposition forces in and around Aleppo and elsewhere. If Hezbollah failed to withdraw, the United States would then need to be ready to attack as soon as the ultimatum expired.
Hezbollah’s withdrawal or US targeting of Hezbollah would send a strong but still limited message to the Syrian opposition and its allies in Turkey and the Persian Gulf, as well as to Iran and Russia.
How would the players in Syria react? Hezbollah would likely try to strike at accessible US assets or citizens in neighboring countries, most likely in Lebanon or Iraq. It might also launch rockets into Israel.
The Islamic State, which uses Hezbollah’s involvement in Syria as a recruiting tool, would be undermined.
Russia and Iran could in theory up the ante, escalating their involvement in Syria, but in practice they both appear to be close to the limit of lives and treasure they are willing or able to expend there. Assad would be outraged and promise revenge, but the Syrian government is even more clearly at the limit of its capabilities.
Meanwhile, the non-extremist Syrian opposition would applaud and press hard against the territory where Hezbollah is deployed. Gulf states would likewise welcome the US action and redouble their efforts to support the opposition.
In short, US targeting of Hezbollah would mostly please and embolden Washington’s friends and discomfit its antagonists. It would also reassert US commitment to fighting terrorism of all sorts, renew Washington’s commitment to holding Hezbollah accountable, hasten an end to the Syrian civil war and make a political settlement more likely.