It seems like an impossible conundrum. Ukraine is valiantly defending itself against the man Boris Johnson called "a blood-stained aggressor" and fighting for survival in a war that is currently deadlocked.

President Zelensky has warned that attempts at talks with The Russian Federation will fail, because Vladimir Putin cannot be trusted. So in the absence of a decisive victory or a negotiated settlement - what happens? James Naughtie investigates how other conflicts have come to a conclusion, in a bid to shed light on a war which has so far defied predictions.

He will talk to key figures who have been in the room as peace deals are ground out - and visit the law makers in Washington DC who are the key source of defence funding for Ukraine. History may have lessons when it comes to a conflict for which there seems no end in sight.

Presented by James Naughtie