JERUSALEM — Israel’s cross-border clash with Iranian and Syrian forces on Saturday was a sharp escalation of long-brewing hostilities along its northern frontier — and a bracing alert to those who have focused on other areas of the Syrian civil war, on other aspects of Iran’s strategic assertiveness, or who believed that Israel’s air superiority left it invincible in its own skies.

In the space of several hours, Israel downed what it said was an Iranian drone that had penetrated its airspace, then struck back at what it called the command-and-control center in Syria from which Iran launched the drone. An Israeli F-16, returning from the attack, crashed in northern Israel after coming under heavy Syrian antiaircraft fire — the first Israeli jet downed under enemy fire in decades.

Israel responded with strikes against eight Syrian and four Iranian targets in Syrian territory.

Prime Minister Benjamin Netanyahu described the day’s events as proof of Israel’s resolve. “Yesterday we dealt severe blows to the Iranian and Syrian forces,” he said Sunday. “We made it unequivocally clear to everyone that our rules of action have not changed one bit. We will continue to strike at every attempt to strike at us.”

But strategists and military analysts in Israel did not see things quite so simply. As both sides sift through the debris, here are some important points:

This isn’t over. It’s just beginning.

As the Syrian civil war winds down, a new conflict is emerging among Iran, which appears to want a lasting Syrian base to threaten Israel; Israel, which is determined to prevent this; and the government of President Bashar al-Assad of Syria, which showed renewed confidence in firing on Israel’s warplanes.