What Could Turkey's Latest S-400 Missile Tests Mean?

Turkish President Recep Tayyip #Erdogan confirmed that #Turkey has started testing the Russian-made S-400 defence system, brushing aside US warnings of 'serious consequences.' But what exactly is the S-400 and why does Turkey want to make them operational as soon as possible? Watch other episodes of ‘Double Check’ 👉 http://trt.world/16zr