The McDonnell Douglas’ F4 Phantom was a workhorse of the United States Air Force during the Vietnam War in the 1960s. It was retired from the USAF and the British Royal Air Force some 20 years ago. But the vintage fighter-bomber put in a surprise performance a few days ago over the skies of northern Iraq.

Iranian Air Force Phantoms purchased during the reign of the Shah of Iran, who was overthrown in the revolution of 1979, attacked Islamic State bases in Diyala province near the town of Saadiya, on the frontline between Iraqi forces and Islamic State.

Pentagon officials were quick to deny any coordination with the Iranian strikes. What is beyond any question, however, is that both the United States and Iran are acting in the same military theatre against a common enemy. This despite the fact that they have had no diplomatic relations for more than 30 years and at times have seemed on the brink of war themselves. While there appears not to have been any direct coordination between the two militaries, both air forces almost certainly did coordinate with the Iraqi defense ministry about the attack.

This episode unusual, but it is not unprecedented.

Consider that the U.S. Air Force and the Bashar al-Assad’s Syrian Air Force have been attacking the same target — the Islamic State controlled city of Raqqa, in the east of the country.

Two weeks ago, the two air forces bombed the city — which is the only provincial capital not in government hands — within days of each other. It is interesting to note that Syrian Air Force attacks on Raqqa have been few and far between since it fell, on Jan. 12, to Islamic State.

Are both the Iranians and the Syrians attacks an opportunistic attempt to underline the common enemy that they share with the United States?

Other members of that coalition will have concluded that they are, and will have viewed these developments with concern, if not anger.

At the commencement of the U.S. coalition attacks on Islamic State, several Gulf air forces participated, including the United Arab Emirates and Saudi Arabia. Their participation since has been less evident. And there can be little doubt that the Syrian aerial attack on Raqqa and the Iranian attack on Diyala will be viewed with grave unease among the U.S.’ allies in the Gulf especially if, in the case of Iran, an unspoken alliance with the United States emerges as a result.

Cooperation between Iran and the regimes in Damascus and Baghdad is hardly new. In fact, the alliance between Iran and Syria goes back more than thirty years to the time of Hafez al-Assad, the father of the current Syrian President. It is a crucial alliance, and without it, Iran would not be able to support its critically important Lebanese ally, Hezbollah.

Israel’s 2006 war with Hezbollah, lasting more than a month, could not have been feasible without Iran’s critical arms supplies and technical assistance to its Lebanese ally.

This explains the motive behind the attack inside Syria by Israeli air force jets on Sunday. The first strike targeted warehouses believed to be holding Iranian missile systems destined for the Hezbollah, and a second strike near Dimas, on the highway between Damascus and the Lebanese border, hit a Hezbollah convoy heading towards Lebanon. The Dimas raid also hit an airbase that sheltered advanced Iranian drones. The pro-opposition Syrian Observatory for Human Rights said it had received information that several Hezbollah members were killed in the Dimas strike.

The Beirut Asharq Al-Awsat newspaper quoted unnamed Syrian opposition sources as saying that the targeted area of Dimas was considered a closed military area under the control of the Fourth battalion of the government forces led by Assad’s brother, Maher El-Assad. The attacking aircraft, on both occasions, used Lebanese airspace as a corridor to get close to their targets the question now is whether there will be any retaliation for Sunday’s airstrikes by Hizbullah. The organization has still not commented on the strikes. Given its heavy military involvement inside Syria supporting the regime of Bashar al Assad that would seem unlikely.

Iran’s close relationship with Iraq is a result of the Bush Administration’s overthrow of the regime of Saddam Hussein in 2003. The removal of the Sunni dictator and the collapse of a strong Iraqi state led the way to the empowerment of the Iraqi Shia and a fast developing Teheran – Baghdad axis. Following the fall of Mosul to Islamic State, the military relationship between the two capitals has deepened, with both Washington and Tehran competing to assist the beleaguered Iraqi regime. Iran is known to have supplied Russian built Sukhoi 25 fighters to Iraq and there is a common supposition that these may be flown by Iranian pilots.

This series of events will inevitably complicate US relations with its Gulf allies. Now in its fourth year, the Syrian war shows no sign of resolution and the emergence of ISIS as a major military and political factor in the Middle East can at best only be contained. The chances of a diplomatic breakthrough are close to zero in the Syrian civil war not least because the biggest loser politically is the opposition Syrian National Council. As so often in civil wars, the extreme parties are dominating the stage. In 2015, the Obama administration will not find a let up in pressures in the Middle East.

PHOTO: A Syrian Air Force fighter plane fires rockets during an air strike in the village of Tel Rafat, some 23 miles north of Aleppo, Aug. 9, 2012. REUTERS/Goran Tomasevic

CORRECTION: The headline on an earlier version of this story mistakenly stated that Israel and Iran were both striking the same country.