It was one thing when four decades of quiet were shattered last fall by Syrian shells that strayed across the Israeli-Syrian frontier, but developments over the past few days on the Golan Heights indicate that Israelis may be forced to take defensive action to avoid being dragged into the Syrian civil war.

While Israel has joined the chorus of regional powers calling for Syrian President Bashar al-Assad to go, Israeli security commanders say they are most concerned about the jihadist rebels currently massing on the Syrian side of the 1974 frontier in the absence of Syrian troops.

Two separate attacks carried out Saturday and Sunday from the Syrian side of the frontier targeted Israeli patrols in the occupied Golan. The attacks were apparently deliberate, according to Israeli officials, unlike previous incidents that have taken place since November, and prompted Israel to respond forcefully, launching a Tammuz guided anti-tank missile against a Syrian machine-gun post. It is unknown whether the post was manned by government or rebel troops.

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The attacks also drew a strong warning from the Israeli commander charged with defending the northern frontiers.

Major-General Yair Golan said that "hundreds" of jihadists are now "very active" on the Syrian side of the frontier and the Israel Defence Forces believe these militants will carry out attacks against Israel from the area. To guard against that, the IDF is building a new security fence along the frontier and increasing the size of its forces in the area. They also are looking at applying an old idea to new circumstances.

"One measure we certainly cannot rule out," the general added, "is to create a defensive buffer zone on the other side" of the ceasefire line. Speaking in an interview published Monday in the Yisrael Hayom newspaper, Gen. Golan said such a zone would be built "with [Syrian] interlocutors who have an interest in co-operating with us against other elements who threaten them too."

He compared such a security measure with the buffer zone Israel maintained for 15 years in southern Lebanon with the help of supporters in the so-called South Lebanon Army, a largely Christian militia that shared Israel's opposition to the militant Shia group, Hezbollah.

The buffer in Lebanon, Gen. Golan said, "was one of the most worthwhile security investments ever made by the State of Israel."

And when it comes to creating a similar zone in Syria today, he said, "If the opportunity presents itself – which as yet it has not – Israel shouldn't hesitate to take it." Just who the anti-jihadist interlocutors would be in this case is unclear.

Yisrael Hayom is said to be Israeli Prime Minister Benjamin Netanyahu's favoured news organ. That the groundbreaking Golan interview appeared in its pages gives the comments added significance.

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Israel captured a large part of the Golan Heights from Syria during the Six Day War in 1967, and held the area in a fierce counterattack by Syria in 1973. Since a ceasefire agreement negotiated by then-U.S. secretary of state Henry Kissinger, the frontier has been patrolled by United Nations troops (including Canadian forces from 1974 to 2006) and calm has prevailed along the 75-kilometre frontier until the past few months.

It is noteworthy that many of the Israeli units based on the Golan have recently changed the nature of their training, focusing less on preparing for tank battles, as they've done for years, and more on fighting irregular forces armed with anti-tank weapons.

Military intelligence chief Major-General Aviv Kochavi told a conference in Herzliya last week that the troops are preparing for possible combat against Hezbollah in Lebanon. But the training could just as well apply to Israeli units facing militant jihadists from Syria.

As Gen. Golan also said: "We have to prepare for the scenario that there will be forces trying to steal into the Golan Heights area.

"There is some logic to this," he explained, "as we are fighting over a piece of territory [the Golan Heights] over which there is no international consensus that it belongs to Israel."

It is no accident that this new Israeli concern comes as the Syrian conflict also is spilling over the borders with Lebanon and Jordan.

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In Lebanon, the movement of pro-Assad and anti-Assad fighters in and out of Syria has so shaken the delicate political situation that Lebanese Prime Minister Najib Mikati resigned on the weekend. The Sunni Lebanese politician had the support of Hezbollah when he took office two years ago, but no more, while the main opposition parties, both Sunni and Christian, strongly oppose Hezbollah and its support for the Syrian President.

On the other side of the Golan, Syrian rebels took control of two border crossings into Jordan on Monday, extending the rebels' hold on Syria's southern frontier area, and closing the Jordanian crossings to all traffic, at least for the time being.

There also were reports from Israel Monday that an al-Qaeda-linked group has seized control of the area west of those border crossings, where the borders of Syria, Jordan and Israel meet, a strategically important area.

Elements of the Islamic militant group the al-Nusra Front captured the area Monday after a battle waged with the Syrian Army's 5th Division, according to DEBKAfile, a right-wing Israeli research group.

Such a development would not surprise the Israeli military command.

However strong Mr. al-Assad's command structure is, the Syrian President has "lost his borders," said Gen. Golan. "Everything is wide open. The northern border is split between Sunni and Kurd zones. The borders with Iraq, Turkey, Lebanon and Jordan are wide open. This makes it hard for Assad to isolate the rebels who, in turn, are receiving massive outside assistance in manpower and munitions."

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And that creates a danger for Israel.