The war in Ukraine has entered another grim milestone. The conflict has now lasted longer than the first world war, underscoring how a war that many expected to end in weeks has evolved into one of the longest and deadliest conflicts in modern European history. Four years on, the displacement and the destruction keep climbing. This week's special Faultlines edition peels back the layers of the root cause behind the war stretching for so long, and with no end in sight.