The undeclared war between Israel and Iran is heating up as, in a nearly unprecedented move, the Israeli government announced that it had struck Iranian targets in Syria.

Iranian troops belonging to the Quds Force were hit along with targets near the Damascus airport.

We have started striking Iranian Quds targets in Syrian territory. We warn the Syrian Armed Forces against attempting to harm Israeli forces or territory.

— Israel Defense Forces (@IDF) January 20, 2019

The Quds Force is an elite unit of Iran's Revolutionary Guards that operates almost exclusively on foreign soil.  Iran deployed the Quds Force to work closely with the Lebanese terrorist group Hezb'allah, whose militia has made a decisive difference in the Syrian civil war.

Despite the winding down of the civil war, Iran and its Hezb'allah allies have not withdrawn and are, in fact, building permanent bases from which most analysts believe they intend to strike Israel in the future.

Fox News:

Until now Israel largely has refrained from public admissions of its covert military operations in neighboring Syria to avoid large-scale involvement in the eight-year civil war.

The military's statement was issued hours after Israeli missile defenses intercepted an incoming missile over the Golan Heights in the wake of rare daylight air raid near the Damascus International Airport.

The Israeli military initially had declined to comment on the airstrike, though it said a rocket fired at the Israeli-occupied Golan Heights was intercepted by Israel's Iron Dome defense system.

Israeli warplanes have used Lebanon's airspace recently to strike deep inside Syria, including attacking a warehouse near Damascus International Airport earlier this month, according to Syrian state media.

The Syrian military said Israel carried out intensive airstrikes with successive waves of guided missiles shortly after 1 a.m., but added that Syrian air defenses destroyed most of the missiles before they reached their targets.

Why go public with news of the strike now?  According to the Fox News report, the Israelis have been increasing their attacks on Iran in recent months:

Israeli Prime Minister Benjamin Netanyahu recently confirmed that Israel had struck hundreds of targets in Syria linked to Iran and the Lebanese Hezbollah militant group, including a weapons facility two weeks ago.  Iran and Hezbollah are allied with the Syrian government in the civil war.

Two hours after the reports that Israel's Iron Dome intercepted a rocket fired toward the Golan Heights, Netanyahu, who currently is on a visit to Chad, said in a statement: "We have a defined policy: to harm Iranian entrenchment in Syria and to harm anyone who tries to harm us."

This is not an escalation.  But it may be a warning to Iran.  Tehran's efforts to effect a military buildup in Syria are simply intolerable to Israel.  The Iranian missile threat is real and growing as Tehran perfects its ballistic missile systems.  Hezb'allah has virtually taken over the government of Israel's neighbor Lebanon and represents a serious threat with its own arsenal of missiles.

Together, Iran and Hezb'allah represent an existential threat to the Jewish state. Israel may be hoping that sounding the alarm that the conflict with Iran is becoming more serious might result in international pressure – especially from the Russians – being brought to bear on Tehran. 

There's always a chance the conflict could get out of hand and become a regional conflict.  Neither side wants that, so for the moment, the strike-counterstrike undeclared war will continue.