Syrian Kurdish fighters have cut an important Isis supply line from Syria to Iraq as they expand an offensive launched in northeast Syria at the weekend that is receiving heavy support from American air strikes.
The seizure of at least 90 Christian hostages from Assyrian villages by Isis (Islamic State) may be its response to the Kurdish attack.
An important aspect of the Kurdish offensive by the People's Protection Units (YPG) is that it is receiving air cover with US Central Command recording 21 air strikes in two days against Isis ground positions and vehicles.
The US is now co-operating militarily with the YPG, which it once viewed as part of a terrorist movement, as a major ally in the war against Isis in Syria. The US only started intense bombing in support of the YPG in mid-October when it appeared the Syrian Kurdish town of Kobane was about to fall to an Isis offensive.
For the first time there is evidence that this military co-operation between the Syrian Kurds and the US is continuing in offensive operations.
The Syrian Observatory for Human Rights says Isis has lost 132 fighters in Hasaka province since February 21, while only seven YPG fighters have been killed, including one foreigner. The disparity in casualties can only be explained by the extensive use of US airpower.
"This is an important development," says veteran Syrian Kurdish leader, Omar Sheikhmous. "It means that the PYD [the political arm of YPG] has reached an understanding with the US about co-operation." Joint action already appears to be showing dividends in fighting around the Isis stronghold of Tal Hamis, east of Hasaka, where Isis is being driven back and has lost control of the road leading to the village of al-Houl and the Iraqi border.
The PYD and the YPG are the Syrian branch of the Kurdistan Workers' Party of Turkey (PKK) which Turkey and the US denigrate as a terrorist organisation. Sheikhmous says the US may have a tactical deal with the PYD but "it deals indirectly with it through the Iraqi Kurdish political parties". An alliance with the militarily formidable Syrian Kurds solves some difficulties with the US, which in theory is planning to build up a force of "moderate" Syrian rebels to fight both Isis and the Syrian Government. The 2.2 million Kurds make up 10 per cent of Syria's population.
The YPG is the toughest fighting force confronting Isis and its advances in northeast Syria will cause problems for the self-declared "Caliphate". Its ability to move forces between Syria and Iraq is disrupted and, in the longer term, Sheikhmous says its control of important oil wells in Deir Ezzor province and positions on the Turkish border are threatened.
But Isis has a track record of responding to military setbacks by acts of violence against civilians to show they are still to be feared. This may explain why early on Tuesday its fighters swept into Assyrian Christian villages and kidnapped between 90 and 200 inhabitants. George Oshana, a 23-year-old university student, speaking by phone from Tal Tamir which is close to the villages where the abductions took place, said "some of the captured are my relatives who were living in the villages between Hasaka city and Tal Tamir. They [Isis] burnt churches, considered the most ancient in Syria, as well as houses.
"I am still worried about the captured people. It is said there might be a genocide. Isis considers Assyrians pagans even though they are Christians."
The Assyrians living in 36 villages on the Khabour River are the descendants of the survivors of the Turkish Genocide of 1915-1918 and a further massacre in northern Iraq in 1933.
Oshana said when Isis captured the villages they blew up the mobile phone masts. Isis has always been fearful that people will use mobile phones to give away their location and enable US drones and aircraft to attack them.
Flight to refuge
• 1000 families have fled villages in the northeastern province of Hasaka since Tuesday's kidnappings, according to the Assyrian Human Rights Network
• 800 of them have taken refuge in the city of Hasaka and 150 in Qamishli, a Kurdish city on the Turkish border
• 5000 people displaced in total, the group said
• An Australian man known as Heval Bagok Serhed has died fighting for the Kurds battling Isis near Tal Hamis in Hasaka province
• YPG units are believed to include people from Canada, the United States, Britain, Spain, Holland, Austria, France as well as Australia.
- AAP, AFP