Israel and Jordan have an odd relationship. The two countries fought a war in 1967, made peace in 1994 and now share mutual worry...

Israel and Jordan have an odd relationship. The two countries fought a war in 1967, made peace in 1994 and now share mutual worry about Islamic State rampaging across the region.

For Israel, the stability of Jordan concerns the security of both countries. In Jordan, there’s growing fear that the terror group will threaten its frontier, and the Hashemite monarchy has embarked on a major military build-up along the Syrian border.

Amman’s warplanes fly in the coalition air campaign over the country. Jordanian officials have shifted their language to emphasize “deterrence” in addition to “defense”–which implies a more active role for the military. There’s even rumors of Jordan establishing a buffer zone inside Syria in support of opposition fighters.

Quietly, Israel is helping to make this possible. In 2014, Israel secretly donated 16 decommissioned Cobra helicopter gunships to Jordan to help it defend its northern border. If Jordan were to go further and establish a buffer zone, the helicopters–which can fire missiles, rockets and cannons–could serve as a valuable hardware.

To be sure, the Cobras–which originally date to the 1960s–deserve some skepticism. They’re quite old, and Israel prefers the sturdier Apache for its own use. Jordan could end up cannibalizing some of the helicopters for spare parts to keep the country’s existing fleet of around 25 Cobras operational.

Either way, the donation is significant, and it’s a sign of converging Israeli and Jordanian interests. There’s a long, complicated history here.

In 1967, Jordan shelled West Jerusalem after the beginning of the Six Day War, which then provoked Israel to seize the West Bank. Nevertheless, Israel helped save Jordan less than three years later from a Syrian intervention that threatened to topple the monarchy.

In September 1970, the Palestine Liberation Organization challenged Jordanian King Hussein Bin Talal’s rule. Violent clashes and a Jordanian crackdown resulted in Syria invading with 300 tanks on the side of the PLO.

The Syrian invasion force, known as the “Palestine Liberation Army,” never amounted to anything more than a Damascus-controlled proxy.

The Jordanians fought a desperate battle to keep the tanks–mostly T-54 and T55s–from reaching Amman. The Syrian advance slowed as maintenance and logistical problems plagued the invading force.

Still, the tanks kept coming.

Hussein was wary of openly asking for Israeli assistance even on an ad-hoc basis. Forming an open alliance with Israel would have irreparably tarnished his image in the eyes of the Arab world.

Nevertheless, the Israeli intervention came. A conspicuous overflight of Israeli Air Force F-4 fighter-bombers warned off the advancing tanks. Since the Syrians hadn’t sent in any air cover, the tanks were sitting ducks.

“Fly over them, leave no doubt that they see you and hear you,” the IAF’s then commander Mordechai Hod recalled in a 1999 PBS documentary. “Make mock attacks so they understand what we want them to do, which is to turn around and go back.”

He attributed the Syrian withdrawal to a mere four Israeli Phantoms flying over the tanks. “A quartet of Phantoms was enough,” Hod said. Jordan successfully suppressed the Palestinian uprising.

A lot has changed in the last 45 years, but Israel has insisted that if Jordan were to come under attack from Islamists in either Iraq or Syria, it would intervene. The delivery of gunships, even if they are older models Israel no longer needs or wants, is considerable.

Members of Israel’s Druze minority has called upon the Israeli military to intervene to protect the Syrian Druze from attacks by the Nusra Front or Islamic State. This has led to discussion and debate in Israel over the feasibility, practicality and possibility of such an undertaking.

Israel has sporadically intervened in Syria. The IAF has bombed Syrian missile shipments, which Tel Aviv feared could end up in the hands of Hezbollah. Israel has also treated opposition fighters in Israeli army field hospitals in the Golan Heights–treatment conditioned upon those fighters ensuring that the Nusra Front doesn’t make any moves against the Druze community.

But Israel faces huge risks intervening further. It could end up in a shooting war with the rebels, the regime or both. Jordan has more political flexibility.

For example, Syria has called on Jordan to support its war with the rebels. It wouldn’t dare ask Israel to do that. It’s possible Jordan could move into Syria and protect the Druze without triggering a clash with the regime–provided it doesn’t support fighters attempting to overthrow it.