Russia's completion this month of an integrated air defence system in Syria has made an Obama administration decision to strike Syrian government installations from the air even less likely than it has been for years, and has created a substantial obstacle to the Syrian safe zones both Hillary Clinton and Donald Trump have advocated. Deployment of mobile and interchangeable S-400 and S-300 missile batteries, along with other short-range systems, now gives Russia the ability to shoot down planes and cruise missiles over at least 400km in all directions from western Syria, covering virtually all of that country as well as significant portions of Turkey, Israel, Jordan and the eastern Mediterranean.