Vladimir Putin has agreed to a ceasefire in Ukraine. Past experience says the Russian president will not keep his promises. Mr Putin’s aim is to disarm the west. The west must decide whether to arm Ukraine.

For old hands at the Munich Security conference this month the argument about whether to supply defensive weapons to Kiev carried echoes of the 1990s Balkan wars. Then the Bosnians were overrun by marauding Serbs. Now Ukraine is buckling under the military might of a revanchist Russia.

The debate has simmered since Moscow’s annexation of Crimea and the dispatch of Russian forces to mobilise separatists in eastern Ukraine. No one could disagree with Angela Merkel, German chancellor, when she said Russian aggression was a profound threat to the European order. Where many parted company with her was in the conclusion that diplomacy and sanctions should mark the limit of the west’s response.