Israel predicted early on that these units’ guns would eventually be turned against it. But in those days, the Islamic State was seen as the embodiment of all evil and accordingly anyone fighting it was one of the good guys. No one heeded Israel’s warnings.

For its part, Israel has conducted more than 100 bombing and missile raids in Syria, without ever admitting it or taking responsibility, against storage sites for weapons and convoys supplying the Iranian-led forces.

With the Syrian Army itself extended to its limits combating rebels, and the Iranians and Hezbollah helping it in the heavy fighting, this tripartite alliance was forced to swallow time after time some bitter truths: They recognized that Mossad and Israeli military intelligence knew how, where and when they were operating, and they knew that they wouldn’t be able to respond to the Israeli raids without suffering heavy losses.

When Russian forces entered Syria in 2015 and it became clear that the United States would not take real measures to counter Mr. Putin’s moves, Mr. Netanyahu managed to set up a secret communications channel between himself and the Russian president, according to my sources in Israeli intelligence, as well as an encrypted phone line for communication between Israel and the Russian military and intelligence in order to prevent clashes between Israeli and Russian forces in Syria.

But that limited amount of tactical coordination hasn’t led Russia to understand Israel’s strategic needs. As an Assad victory approaches, Israel has been asking Russia to guarantee that the Iranians will leave Syria once the war is over. Those requests have been met with indifference in Moscow. Russia wants to build a secure foothold in the Middle East and its policy requires it to maintain good relations with Iran.

Israel has also asked the Trump administration several times to do something to stop the situation from deteriorating. Last August, a high-ranking delegation visited Washington, including Yossi Cohen, the director of the Mossad, and Herzl Halevi, the head of Israeli military intelligence. They presented H. R. McMaster, Mr. Trump’s national security adviser, with, according to my sources, “sensitive intelligence material, credible and of great concern” about Iranian and Hezbollah plans to attack Israel on the border with Syria. Hezbollah, they said, was building a significant military presence in Syria and Iran was planning to set up a naval base on the Mediterranean at the port of Tartus.