On one hand, the Czechs have pioneered a plan to surge desperately needed artillery shells to Ukraine’s front lines, sourcing munitions from the arsenals of countries around the world. On the other, Fico, a populist and four-term prime minister who returned to power at the end of last year after a spell in opposition, has suspended military assistance to Ukraine after campaigning to not send “another bullet” to Kyiv. He has repeatedly called for the war to end with significant Ukrainian concessions to Russia.

The gulf between the two governments grew this month, after Prague suspended a tradition of informal joint cabinet meetings with Bratislava in the wake of a meeting between the Slovak foreign minister and his Russian counterpart, Sergei Lavrov. Fico’s self-styled “sovereign” foreign policy is similar to the position struck out by his ally in Hungary, illiberal Prime Minister Viktor Orban, who has a close relationship with Russian President Vladimir Putin. Fico has not played the same obstinate role as Orban on the European Union level but has nevertheless bucked the trend among Ukraine’s European neighbors in wholeheartedly backing its defense.

“I think I can say there are differences among us,” Czech Prime Minister Petr Fiala said at the sidelines of meetings at the end of February of a four-nation bloc comprising his country, Slovakia, Poland and Hungary. “I won’t keep it secret, it wouldn’t make sense, that we differ in the views of the cause of the Russian aggression against Ukraine and the ways of solving it.”

Since the end of the Cold War and the subsequent bifurcation of Czechoslovakia, the two countries that emerged maintained warm brotherly ties, even when ruling governments in Prague and Bratislava were of differing political stripes. But disagreements over how or how not to support Ukraine have brought about an unprecedented rupture. “Even at its worst in the past, the relationship was one of mutual indifference but never one of open rhetorical confrontation,” Dalibor Rohac, a senior fellow at the American Enterprise Institute, told me.

Fico responded to Fiala’s decision to suspend those intergovernmental consultations between the two countries’ cabinets by accusing Fiala’s government of jeopardizing ties with their historic brethren and having “an interest in supporting the war” in Ukraine. Fiala then pointedly hosted Michal Simecka, the Slovak opposition leader, in Prague and hailed their shared views on foreign policy.

“We know who is the aggressor and who is the victim, and we also know who needs to be helped,” Fiala said in a reference to Putin’s invasion of Ukraine.

Fico has been outspoken in his challenges to Western orthodoxy, offering the perspective of a supposed pragmatist who wants peace and recognizes Ukraine will not be able to recover much of the territory it has lost in the south and southeast of the country. He also casts overt support for Ukraine as a bid to undermine Russia and has mocked the idea of Ukrainian sovereignty, suggesting Kyiv is entirely beholden to the United States.

“I am not convinced of the sincerity of the West to achieve peace in Ukraine,” Fico said on Facebook this month. “And I will repeat again that the western strategy of using the war in Ukraine to weaken Russia economically, militarily and politically is not working.”

The tensions on show may be less about divisions between the two countries than those within them. Fiala’s predecessor, Andrej Babis, is similarly aligned with Fico’s camp, a populist wary of E.U. diktat and more friendly to Moscow. In both countries, a critical mass — though not the majority — of the electorate is skeptical of the West and open to the Russian perspective of the war.

“When Fiala rebuked Fico, he was also rebuking Andrej Babis and the various pro-Kremlin voices at home,” Rohac told me. “The difference between Fiala and Fico is that the former sees the war in Ukraine as existential. The latter, meanwhile, sees it as a purely external event that can be used instrumentally to pursue his political ends at home — just like Babis.”

In January 2023, Babis suffered a major defeat in presidential polls, losing by a considerable margin to pro-Western former general Petr Pavel. But Peter Pellegrini, another former prime minister and Fico ally, is the front-runner for the presidency of Slovakia, which will stage first-round elections this weekend.

That may have deeper consequences at a time when Fico’s opponents are warning of his efforts to tighten his grip on power and undermine checks and balances in the furtherance of his interests and those of a set of oligarchic allies. The presidents in the Czech Republic and Slovakia play a largely symbolic role but have the ability to check parliamentary maneuvers and legislation.

A Pellegrini victory “would further weaken checks and balances in Slovakia and deprive the country of an important monitor of democracy, in a region struggling with democratic backsliding,” observed Barbara Piotrowska, a lecturer at King’s College London. She added that, combined with Fico’s return to power and Orban’s imperious reign in Budapest, this would send “a strong signal that the situation in the region is far from stable and democracy remains fragile” and put Slovakia on “a collision course” with the E.U.

Slovakia’s closest neighbors are concerned. “We are worried that Slovakia is on the wrong path,” a Czech official told Britain’s Guardian newspaper on the condition of anonymity.