From the rooftop of an uninhabited, half-destroyed building a contingent of Ukrainian paratroopers watch the frontline of pro-Russian controlled Donetsk. It is situated in Avdiivka, an industrial town in the middle of the buffer zone where shelling between Kyiv’s forces and pro-Russian separatists has gone on unabated for the past two years – despite a ceasefire established by the Minsk agreement.