April 4: Chemical attack

A rocket laced with the nerve agent sarin kills more than 80 civilians in Khan Shaykhun in the rebel-held Idlib province. The attack is attributed to the government of Bashar al-Assad.  There is reportedly “mounting evidence” that Russia was “complicit” in the attack at least through knowledge or acquiescence.

April 6: Cruise missile response

The U.S. launches 59 Tomahawk cruise missiles at a Syrian government air base.

A Russian spokesman says the strike “deals a significant blow to relations between Russia and America, which are already in a poor state.” Russia says it will strengthen Syria’s air defense systems to “protect the most sensitive Syrian infrastructure facilities,” and will suspend the memorandum of understanding with the U.S. to deconflict airspace to avoid accidents.

May 6: Memorandum of understanding reinstated

Russian and U.S. chiefs of general staff agree to resume implementation of the aircraft safety memorandum of understanding.

May 18: First strike against pro-Syrian government forces at al-Tanf

The Coalition bombs pro-Syrian regime forces that had advanced into the 55-kilometer “de-confliction zone” surrounding al-Tanf, a garrison used by U.S. Special Forces and allies to train Syrian partner forces. “Iranian-directed” militias were building an outpost within the zone, and after failing to deter them by firing a warning shot, U.S. planes bomb a tank, a bulldozer and an excavator.

The following day, chairman of the Joint Chiefs of Staff, General Joseph Dunford, tells reporters the strike was “a force protection strike. Our commanders on the ground felt like they were threatened at that point. And their rules of engagement allow them to do that.”

While the strike stops the forces progressing, they remain “deep” within the de-confliction zone.

Secretary of Defense James Mattis says of the Iranian-directed forces:

“We believe they moved into that zone against the advice of the Russians.  Or — or — you know, apparently against the advice of the Russians.  I can’t confirm that either, but it looks like the Russians tried to dissuade them.”

The U.S. captured the al-Tanf garrison over a year ago and unilaterally declared the territory around it to be a “de-confliction zone”. That zone is not recognized by Russia or the Syrian regime (and should not be confused with the formal de-confliction agreement and hotline established between Russia and U.S.). U.S., British, Norwegian and possibly Jordanian special forces are present at al-Tanf.

The Military Times reports, “U.S. and coalition forces operating at the Tanf training facility use the location to train two partner forces, the Maghawir al-Thawra and Shohada al-Quartayn. CENTCOM contends these groups are anti-ISIS fighters, but in the past they have fought against the Assad regime.”

Defense One notes that on May 18, “Fars, an Iranian news agency affiliated with the Islamic Revolutionary Guard, reported that 3,000 Hezbollah fighters had been sent to Tanf to back the Syrian military in its fight against the United States ‘and establish security at the Palmyra-Baghdad road.’”

Week of May 29: Russia fires on US-supported forces protecting al-Tanf

In the al-Tanf area after repelling pro-regime forces, US-supported forces are reportedly “forced to pull back when they were attacked by Russian aircraft.”

June 6: Second strike against pro-Syrian government forces at al-Tanf

Pro-Syrian regime, Iranian-backed forces advance into the de-confliction zone surrounding the al-Tanf garrison. The Coalition responds by bombing two armed pickup trucks.

The Coalition statement released by CENTCOM says that despite warnings:

“pro-regime forces enter the … zone with a tank, artillery, anti-aircraft weapons, armed technical vehicles and more than 60 soldiers posing a threat to Coalition and partner forces based at the At Tanf Garrison.

The Coalition issued several warnings via the de-confliction line prior to destroying two artillery pieces, an anti-aircraft weapon, and damaging a tank.”

The statement emphasizes that the Coalition does not seek to fight the regime or pro-regime forces, but will defend itself if pro-regime forces refuse to leave the zone.

The Military Times had earlier reported that pro-regime forces did not leave the zone following the May 18 strike, but the CENTCOM statement suggests this was a new entry of forces into the zone.

June 8: U.S. shoots down Iranian-made drone after it drops bomb near U.S. and U.S.-backed forces

A U.S. warplane shoots down a pro-regime drone after it drops a munition near U.S. forces on patrol with U.S.-backed Syrian fighters near the al-Tanf garrison (but outside the de-confliction zone). The drone, a Shahed 129 model made by Iran, was carrying other weapons. U.S. officials say they did not know who directed it.

In a statement, CENTCOM says:

“The Coalition’s mission is to defeat ISIS in Iraq and Syria. The Coalition does not seek to fight Syrian regime, Russian or pro-regime forces partnered with them. The demonstrated hostile intent and actions of pro-regime forces near Coalition and partner forces in southern Syria, however, continue to concern us and the Coalition will take appropriate measures to protect our forces.”

June 8: Syrian warplane intercepted

Later the same day, a Syrian warplane begins maneuvering to bomb the fighters but is intercepted by a U.S. jet. The Syrian airplane, a SU-22, departed, dumping its bombs.

June 18: U.S. plane shoots down Syrian SU-22 plane after it bombs near U.S.-supported forces in Raqqa province

A Syrian SU-22 drops bombs near U.S.-supported local fighters south of Tabqa and is shot down by a U.S. F/A-18 fighter jet. Several fighters are wounded.

A CENTCOM statement says that the move was in “collective self-defense” of Coalition-partnered forces.

“The Coalition presence in Syria address the imminent threat ISIS in Syria poses globally,” the statement also says. “The demonstrated hostile intent and actions of pro-regime forces toward Coalition and partner forces in Syria conducting legitimate counter-ISIS operations will not be tolerated.”

On the same day, Iran launches mid-range missiles from Iran to Syria. The events are believed to be unrelated.

June 19: Russia’s threat to Coalition and hotline suspension

Russia describes the incident as a “flagrant violation of international law.”  Russia threatens to target Coalition aircraft and drones west of the Euphrates. Russia also claims to have suspended the de-confliction hotline used by the American and Russian militaries (although the following day a spokesman for the American-led air war command tells the New York Times that the hotline remains active).

June 20: U.S. shoots down another Iranian-made drone

Another Iranian-made Shahed 129 drone is shot down by a U.S. jet when it approaches the de-confliction zone surrounding the al-Tanf garrison. An official says the drone was “assessed to be a threat.” The American F-15E jet tried to get the drone to change direction before shooting it down, but the drone continued towards the Coalition-backed fighters.

Fars news agency, which is affiliated with the Islamic Revolutionary Guard, writes, “Syrian soldiers and the Lebanese Hezbollah forces have established several fortified positions along the Syrian-Iraqi border in spite of the US-led coalition’s warning and its air raids on army positions in al-Tanf region in Southeastern Homs in May and early June.”

Fars also claims the U.S. is training anti-Assad forces referring to “the al-Tanf border crossing, where the Washington forces are training anti-Syrian government Free Syrian Army (FSA) fighters.” (See May 18 entry for Military Times report that U.S.-backed forces trained at al-Tanf have “fought against the Assad regime” in the past.)

June 20: Iranian drone base near al-Tanf reported

U.S. officials say Iran has established a drone airfield near Palmyra, about 80 miles away from the al-Tanf garrison. Iran has based Shahed 129 drones at the airfield. The officials say it is likely that the drones the U.S. has shot down flew out of the base.

June 21: Australia to resume airstrikes after suspension

After halting its operations in Syria, Australia announces it will resume airstrikes soon. The Australian Defense Ministry had announced on June 20 that six warplanes based in the United Arab Emirates had been suspended from operations “as a precautionary measure,” following Russia’s warning on June 19.


[Editor’s note: For analysis of these and related events, see our coverage of Syria and al-Tanf in particular.]


Photo: Peter Hermes Furian/Getty Images