two top floors of the National Defense Building, known as the Glass House, in Syria, released on November 20, 2019. (ImageSat International)

Israel’s military remains on high alert on the northern front over concerns that Iran might retaliate to the wave of airstrikes against dozens of military targets belonging to the Iranian Quds Force and the Syrian Arab Army on Tuesday night in Syria.Out of concern that Iran might strike Israel in the coming days, perhaps even before the weekend, the IAF has been placed on high alert, and air defense batteries in the North have been reinforced, Channel 12 news reported.IDF Spokesman Brig.-Gen. Hidai Zilberman told reporters on Wednesday that the tens of targets struck in Damascus, west of Damascus and the Syrian Golan Heights overnight, belonging both to the regime of Bashar Assad and the Quds Force, were carried out within minutes. All were located within 80 km. of Israel’s border.While the launchers which fired the rockets on Tuesday morning were not struck, some 20 other targets struck included advanced air defense systems (not the Russian-made S-300 missile defense batteries), surface-to-air missiles, reconnaissance sites and warehouses, the National Defense Building at the Damascus International Airport, which houses the Quds Force headquarters, and other military positions.Images released by ImageSat International showed that the two top floors of the National Defense Building, known as the Glass House, were destroyed. The building was where the Quds Force’s Intelligence unit reportedly operated. Following the strike, “the site looks abandoned,” the report stated.“We will not let Iran entrench in Syria ,” Zilberman said, adding that the IDF “is prepared to respond harshly to further attacks if necessary. We will not accept an Iranian force near our borders, and will continue to work against it.”According to the British-based Syrian Observatory for Human Rights, 23 people, including 16 non-Syrians, most likely Iranians, were killed in the Israeli airstrikes. A senior Israeli defense official acknowledged that there were wounded and a number of Iranian fatalities. Numerous others were wounded, including a young woman who was wounded by shrapnel that hit the suburb of Qudsaya, west of Damascus.Local Syrian media reported that two residential buildings were also struck from shrapnel from a Syrian air defense missile fired toward Israeli jets, hospitalizing one family, including two children.“We express the wish for a speedy recovery for them,” the Assad government said in a statement carried by state news agency SANA. Damascus promised to provide assistance to those who suffered the “brutal Israeli aggression” by repairing the homes of those affected.It said help would arrive immediately to those areas struck, with rescue teams sent to clear rubble in the area of Sasa south of Damascus, where a house was destroyed. Ambulances and fire engines were sent to other areas.“During the attack, Syrian air missiles were fired, despite a clear warning that was ignored. As a result, several Syrian aerial defense batteries were destroyed,” the IDF said.While the main targets were Iranian, the official said, secondary goals included six air-to-ground missile batteries belonging to the Syrian regime “to maintain freedom of action and protect our pilots.”Defense Minister Naftali Bennett said following the strikes that “the rules have changed: Anyone who shoots at the State of Israel during the day will not sleep at night. Like last week and now this week. Our message to Iran’s leaders is simple: You are no longer immune. Wherever you stretch your tentacles – we will hack them off. The IDF will continue to protect Israeli citizens.”According to a senior official in Israel’s defense establishment, the “head of the Iranian octopus” sits in Tehran but continues to attempt to surround Israel with proxy groups – Hezbollah in Lebanon, Iranian militias in Syria, Palestinian Islamic Jihad (PIJ) in Gaza and, to some extent, Hamas.“We have not yet threatened the head of the octopus - Tehran. But it is possible to start approaching the head of the Iranian octopus,” he warned.Israel’s military said the Russians were told of the strikes through the deconfliction mechanism, but Russian Deputy Foreign Minister Mikhail Bogdanov said that the strikes were a wrong move, and Moscow contacted its allies about the incident, Interfax reported.According to the senior Israeli defense official, the strikes were one of the largest that struck Iranian targets in Syria, and was finalized Tuesday night by Prime Minister Benjamin Netanyahu in Jerusalem, and Bennett and IDF Chief of Staff Lt.-Gen. Aviv Kochavi at the Kirya military headquarters in Tel Aviv.“Iran struck Israel. We can’t forget that. Iran attacked Israel, and that’s not acceptable,” he continued, saying that Israel will strike harshly, without giving any warning, if attacked in the future.“We are changing the rules. Even when it comes to almost negligible attacks, whose impact is small, we are changing the equation, and our retaliatory attack will be widespread. When I looked at the south, when a small number of rockets are fired and we respond with a small retaliatory strike, then that sort of situation gets to be acceptable. We have to strike harshly [in response] to all attacks,” the official said, noting the link of the assassination of PIJ leader Bahaa Abu al-Ata in Gaza and the rockets of yesterday.On Wednesday, the commander of the Bashan Brigade, Brig.-Gen. Amit Fisher, and other senior officers from the Golan Brigade and Home Front Command met with heads of the Golan and Hermon regional councils to update them on the situation and continued cooperation between the military and civilian bodies in the area.“We have set ourselves the goal of preventing Iranian consolidation in Syria, and we are working toward that goal. For the past year and a half, we have been dealing with rocket fire by Iran toward the State of Israel,” Fisher said.“The IDF is constantly monitoring operations by the Iranian establishment in Syria, and we will continue to be prepared for every scenario,” he said, adding that the military reinforced air defense systems and is “constantly working” to enable residents to return to their normal routines.While the IDF spokesman stressed that no special instructions for the North have been given, the military was prepared for three possible scenarios: no response, a minor response, and a more significant response.“The IDF is highly prepared for a variety of scenarios, and will continue to operate as required for the security of the citizens of the State of Israel. The Home Front Command instructions should be obeyed if required.”The strike, which began around 1 a.m. on Wednesday, was carried out in response to four rockets that the IDF said were launched by an Iranian force from Syria toward northern Israel in the early hours of Tuesday morning.All rockets were intercepted by the Iron Dome missile defense system, causing no damage or injuries.“The Iranian attack against Israeli territory yesterday is further proof of the current Iranian purpose in Syria. Their presence in the region is a danger to Israel’s security, regional stability and to the Syrian regime,” the military said.Netanyahu issued a statement following the attack, saying: “I made it clear that whoever harms us, we will harm them. That is what we did tonight in Syria against Iranian Quds Force targets and Syrian military targets, after rockets were fired from its territory towards Israel. We will continue to aggressively guard the security of Israel.”Syrian news agency SANA reported that Syrian regime air defense systems were able to intercept 11 of the 18 missiles fired by six jets before they struck their targets.According to SANA, regime defenses came under “a heavy attack” by IAF fighter jets that targeted the Damascus area from the Israeli Golan Heights and Lebanese airspace near the town of Marjayoun.Israel has been carrying out a war-between-wars campaign since 2013, in an attempt to prevent Iran and its proxies, including Hezbollah, from obtaining advanced weapons to use against the Jewish state and from entrenching themselves in Syria.Thousands of strikes have been carried out over the years in Syria and, according to foreign reports, in neighboring Iraq.Kochavi and Netanyahu have warned in recent weeks of the increased threat posed by the Islamic Republic, which they say is becoming bolder and more willing to respond to Israeli attacks on Iranian and Iranian-backed militias and infrastructure.Seth J. Frantzman contributed to this report.