Ukraine will be “forced to take retaliatory measures” if Poland passes a bill equating the Ukrainian nationalist movement with Nazism and communism, Ukrainian historians said on October 1.

The episode marks the latest flare-up in tensions between the two allies over the legacy of the Second World War and the Volhynia massacres, in which around 100,000 ethnic Poles were killed by Ukrainian nationalists.

Nawrocki this week submitted legislation that would expand Poland’s criminal code, which already bans the promotion of Nazi, communist, fascist and other totalitarian systems with penalties of up to three years in prison. 

The president’s bill would add to the list the ideologies of the Ukrainian Insurgent Army (UPA) and a faction of the Organisation of Ukrainian Nationalists led by Stepan Bandera.

The UPA and OUN-B, which were interlinked groups fighting for Ukrainian independence during the Second World War, are accused of atrocities against Poles and Jews.

Poland recognises the Volhynia killings as genocide. Ukraine rejects that label and continues to honour figures from both movements, drawing long-standing criticism from Warsaw and Israel.

“To eliminate Russian propaganda and establish Polish-Ukrainian relations based on real partnership, mutual respect and mutual sensitivity, I believe we should … equate Banderite symbols in the penal code with symbols that correspond to German Nazism and Soviet Communism,” Nawrocki said in September.

In a statement signed by 40 Ukrainian historians and circulated by the Ukrainian embassy, the Ukrainian side said it is “concerned” by attempts to equate UPA and OUN-B with totalitarian regimes.

The statement also accused Polish politicians of placing sole blame for the Volhynia tragedy on Ukrainians. They urged the bill’s backers to “avoid politicising the issue”.

If the bill is adopted in Poland, Kyiv would likely feel compelled to retaliate by passing its own legislation condemning the actions of Polish resistance units, the historians' statement said.

Those units were responsible for atrocities against Ukrainian civilians during the Second World War and the immediate postwar years, they also said.

“Given Russia’s ongoing aggression against Ukraine and the entire civilised international community, we consider as unacceptable actions that weaken Ukraine, and thus Poland, precisely because this constitutes the strategic goal of the Russian aggressor, who for centuries has done everything to destroy both Ukrainians and Poles,” the historians said.