While Moscow is still awaiting a credible explanation from Turkish authorities for their decision to down a Russian fighter jet, Ankara still refuses to apologize. In response, Russia is adopting a series of measures against Turkey and will send S-300 and S-400 antiaircraft to Syria, the latter among the world's most powerful. Why Turkey chose to down the Russian plane and send supplies to forces Syria considers to be terrorist is a question that remains to be answered. Hazem Abdullah reports from Damascus. teleSUR