Why is NATO member Turkey acting with Russia in Syria?

The Turkish military announced on Dec. 30 that Russian jets hit positions of the Islamic State of Iraq and the Levant (ISIL) near the Syrian town of al-Bab. 

Official sources say the ISIL targets were marked by Turkish Special Forces carrying out an operation to take the town from ISIL hands. Military sources also said they hit an ISIL convoy and an ISIL chief named Abu Husen Tunusi was in the destroyed convoy in air raids on Dec. 29. They added that Tunusi and his team were sent by ISIL to al-Bab from Raqqa as reinforcements.

It seems that the operation or operations took place right after statements on Dec. 29 in Ankara, Moscow and Damascus about the declaration of a ceasefire between forces loyal to the Bashar al-Assad regime in Syria and against it from midnight on Dec. 29. Turkey and Russia are acting as guarantors of the cease-fire, which excludes the forces of ISIL and al-Nusra.

The announcement on Dec. 30 raises the bar of the military cooperation between Russia and Turkey, a member of NATO and also a member of the U.S.-led coalition against ISIL. It also comes at a time when tension between the U.S. and Russia is rising on security and intelligence matters.

On the day when the ceasefire in the nearly six-year-old Syrian civil war was announced, the outgoing Barack Obama administration in the U.S. declared 35 Russian diplomats "persona non grata" over cyber-security and intelligence crimes and asked them to leave the country within three days. The next day, on Dec. 30, Russia moved to expel 35 American diplomats from Russia in retaliation. These were typical Cold War moves, rarely seen since the disintegration of the Soviet Union in 1992. When combined with Obama's recent move against Israel at the U.N., despite the $38...