In addition to one or two thousand Iranian troops in Syria, Tehran also has at under its command some 100,000 Syrian militiamen and 20,000-25,000 fighters from Lebanon, Iraq, Afghanistan, and Pakistan. The Islamic Republic has also successfully completed a land bridge running from its borders, through Iraq and Syria, to Lebanon; it now plans to build air, naval, and land bases in Syrian territory. Thus far, Israel has effectively used airstrikes and artillery fire to enforce its red lines in Syria, but, argues Michael Herzog, the ayatollahs may soon become bolder about striking back:
For Israel, the risk of escalation in Syria has remained low so long as the war raged and the relevant actors were heavily enough involved that they could not afford to open another front with Israel. . . . But such risk of escalation is likely to increase as the war nears an end, de-escalation and political solutions dictate the agenda, an emboldened Syrian regime regains control over most of the country, and Iran entrenches itself more deeply in the area. In such a context, Israeli preventive measures are likely to incur bold responses from the Iran-Syria camp, and possibly Russian pressure for Israeli restraint so as to avoid escalation and the undermining of a Russian-led political process.
Indeed, earlier in 2017, the Syrian regime began responding to perceived Israeli strikes by firing in the direction of Israeli planes. While not endangering the planes, these actions signaled growing boldness and a greater inclination to respond, prompting an Israeli decision to retaliate to any such firing, with the aim of definitively protecting its freedom of operation, including against the introduction and use of sophisticated air-defense capabilities—another Israeli red line. . . .
One [can reasonably] assume that Iran and Syria are now seeking ways to create counter-deterrence vis-à-vis Israel, which in turn could add fuel to the sizzling fire. . . . [A]s the risks of friction with Iran grow in Syria, Israel will have to assess more carefully the delicate balance of deterrence in order to avert both a major military escalation [and Russia turning against the Jewish state]—both highly undesired outcomes from Israel’s standpoint. A growing challenge to Israel’s stated red lines will call for a more conscientious definition of what constitutes a real, not rhetorical, red line whose violation would justify action even at the risk of major military escalation [with Iran and its proxies] or tension with Russia. If Israel feels a certain Iranian move is likely to develop into an intolerable challenge in a future confrontation with Iran and Hizballah, it would likely take action and risk confrontation now, on better terms, rather than later. . . .
Ultimately, [however], countering Iranian plans in Syria would be much easier and more effective if Israel’s deterrent actions fit within a broader, proactive U.S. strategy to block Iran in the region, rather than Israel shouldering most of the burden alone.