The alliance between Ukraine and Poland, which looked unshakeable while Russian tanks were on Ukrainian territory, has suddenly begun to crack - and not over the present, but over a bloody past from more than eight decades ago.

The spark is seemingly symbolic: Ukrainian President Zelensky approved a military unit to bear the honorary name „Heroes of the UPA" - the Ukrainian Insurgent Army. For Poland this is an insult, because the UPA there is linked to the massacres of the Polish civilian population in Volhynia during the Second World War. On 11 July 1943, UPA units attacked over 150 villages; historians estimate that between 60,000 and 100,000 Polish civilians died, and another 10,000 to 15,000 Ukrainians in the Polish reprisals. The Polish parliament declared those events a genocide in 2016.

The reaction was swift and sharp. Polish President Nawrocki launched a procedure to strip Zelensky of Poland's highest decoration, the Order of the White Eagle. Zelensky shot back that he would return the medal himself, by post, to Warsaw. Three former Ukrainian presidents joined the protest, while opposition leader Kaczyński threatened to block the negotiations on Ukraine's EU accession.

Behind the historical dispute lies a far more contemporary calculation. Polish enthusiasm for Ukrainian refugees has waned, farmers are in revolt, and right-wing parties skilfully ride that fatigue. When the political climate cools, old wounds suddenly become a useful weapon. The Balkans know this by heart - here, history is never a closed subject, but a reserve drawn upon exactly when someone needs it. The question is whether Europe has truly changed, or has merely learned to package the same old hatreds more politely.