David A. Andelman, executive director of The RedLines Project, is a contributor to CNN, where his columns won the Deadline Club Award for Best Opinion Writing. Author of "A Shattered Peace: Versailles 1919 and the Price We Pay Today," he was formerly a foreign correspondent for The New York Times and CBS News. Follow him on Twitter @DavidAndelman. The views expressed in this commentary are his own. View more opinion on CNN.

(CNN) With a single stroke, President Donald Trump has effectively brought a newly resurgent and potent triad—Syria, Russia and Iran—to the very doorstep of their declared enemy, Israel, and given aid and comfort to Israel's longtime and persistent foe, Hezbollah, in Lebanon.

David Andelman

The ceasefire and agreement with Turkey that Trump vaunted Thursday as "a great day for civilization," had already been demonstrated to be a potentially epic challenge to one corner of the world—Israel. It was a reality only highlighted by Secretary of State Mike Pompeo breaking off from Vice President Pence's group in Ankara and taking a plane directly to Jerusalem to reassure Prime Minister Benjamin Netanyahu Friday morning.

Suddenly, with not even a token American force remaining to monitor or check military activities of Russia, Iran or the Syrian army main force of President Bashar al-Assad, the entire map of the Middle East was being redrawn, and Israel left with few viable defenders. When the United States had even a minimal military presence in Syria, it was able to act as some restraint on aid that Iran was seeking to channel to this terrorist force which continues to operate out of Lebanon , targeting Israel at every opportunity.

In late August, anti-tank rocket attacks launched from Lebanon into northern Israel by Hezbollah led to the Israeli army responding with attacks on targets in southern Lebanon. Such effective shadow-boxing had been held in check by the apparent ability of Israel to interdict Iranian efforts to supply Hezbollah with arms and munitions through Syria. Now, with Syria reclaiming a large swath of the northeastern stretch of its country that had been held by the Kurds and their American allies, and with Russian forces moving as a backstop into the vacuum left by the US departure, Israeli efforts could become exponentially more complicated.

At the same time, there is ever more leeway now for Syria, Russia and Iran to work their malevolence on a Lebanese government that is striving desperately to carve a middle road in the region. Hezbollah and Iran share a common religion—Shiite Islam—which has only opened up a host of problems for Hezbollah's principal host, Lebanon, as it tries to remain reasonably neutral in the Middle East and avoid a return to the decades of bloodshed during its civil wars of the 1980s. Hezbollah would like nothing better than a destabilized Lebanon bordering Israel's northern frontier.

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