The front line of the war in eastern Ukraine divides towns, villages and even families into Ukrainian territory or rebel territory. On each side, stretching for 15 kilometers, is the internationally-agreed buffer zone - an allegedly demilitarized area created as part of the second Minsk peace deal in February. On a map, the buffer zone straddles the Lugansk and Donetsk Oblasts, changing direction like a snake charting its way through unfamiliar territory.