It has been two years since Russian troops invaded Ukraine, sparking a deadly war that many say is far from over. Western officials have estimated that hundreds of thousands of people have died in the conflict, which has evolved into what experts call the world"s first full-scale drone war, with hundreds of drones firing explosives every day. But in the past 12 months, the frontline has barely moved and some say a stalemate has been reached. The Guardian"s Andrew Roth explains why the frontlines seem to be frozen and why the war drags on