Friday brought good news for those who want Europe’s troubled Southeast to join Western security and political structures. Montenegro’s parliament officially approved the country’s invitation to join the North Atlantic Treaty Organization. It wasn’t a slam-dunk—approval got 46 votes in the 81-member assembly, with opponents boycotting the vote—and joining NATO remains controversial in the tiny Balkan country, but this was unquestionably a setback for the Russians.

Vladimir Putin pushed hard to keep Montenegro out of the Atlantic Alliance, applying the full range of dirty tricks in the Kremlin’s Special War toolbox: espionage, propaganda, subversion, even plotting assassination and terrorism. It didn’t work in the end, indeed a ham-handed scheme by Russian spies to violently overthrow Montenegro’s government last fall probably helped the pro-NATO side in the end.

Kremlin motivations here are anti-Western spite more than rational strategic calculus. Montenegro was never part of either the Tsarist or Soviet empires, and while it’s easy to see why Russians are perturbed by NATO expansion in the former USSR, Moscow’s anger over a tiny country on the other side of Europe seems out of place. Yet, as I’ve previously explained, Putin continues to fret about NATO’s role in the break-up of Yugoslavia a generation ago, which he like many Russians views as some sort of nefarious Western plot. This is pure ressentiment.

The Russians lost this round, however, and Montenegro will soon become NATO’s 29th member, perhaps at the Alliance’s 2017 summit in Brussels in late May. While Montenegro brings little to NATO, strictly speaking—its military is smaller than Baltimore’s police department, and not much better armed—its geostrategic position is important. NATO will now control the entire Adriatic coastline, which has real implications for the security of the Mediterranean and Southern Europe. The country’s key port of Kotor, a protected maritime repair facility long coveted by Moscow, is a definite positive for the Alliance.

Above all, by joining NATO, Montenegro’s strategic value is denied to the Russians. Negative aims can be as important as positive ones in statecraft. This leaves Serbia, which was united with Montenegro in the last vestiges of Yugoslavia until 2006, landlocked and divided politically between East and West. Russophilia is perennial in Belgrade, particularly on the nationalist Right, and Serbia eventually will have to decide if it wants to join NATO and the European Union, or if it prefers Putin as their main partner. If Serbia chooses the latter course, Montenegro belonging to NATO will improve the West’s military and diplomatic position in the region.

The Kremlin predictably is having a tantrum over Montenegro’s Friday vote, with official outlets castigating alleged Western malfeasance in the tiny country, presenting the parliamentary vote as some sort of undemocratic coup. We can expect Russian clandestine harassment to continue—that’s Putin’s go-to solution for any foreign policy problem—but there’s little Moscow can do now to block Montenegro from officially joining NATO.

More serious is the possibility that Russian-backed agitators and provocateurs may foment chaos far beyond Montenegro. Too much of the region remains mired in corruption, criminality and political paralysis, and Balkan countries seem incapable of finding fixes to their intractable problems. The short-term solutions fashioned by Western semi-colonial apparatchiks in the 1990s to manage the wreckage of Yugoslavia are fraying badly. For the first time in the post-9/11 era, a return to widespread chaos and mayhem in Southeastern Europe seems possible.

Take Macedonia, the only country to escape Yugoslavia in the 1990s without violence. A small and impoverished land of two million that stands on the front lines of the EU’s refugee crisis, Macedonia is bitterly divided between its Slavic majority and Albanian minority. How many Albanians there are is a hotly contested question—due to political game-playing there’s been no census in 15 years – but the minority constitutes somewhere between one-quarter and one-third of Macedonia’s population.

Many of them are unhappy with the post-Yugoslav status quo, and an armed Albanian insurgency in the summer of 2001 in northwestern Macedonia nearly exploded into all-out ethnic war. Only strong pressure from NATO and the United States averted disaster. Even then, fighting raged for days in the suburbs of Skopje, the country’s capital. In the aftermath of the 2001 semi-war, Albanians were granted major political concessions, including guaranteed participation in any future Macedonian government.

This all has done little to ameliorate relations between Albanians and Slav Macedonians, not to mention that the country has all the other problems found in the region, too: poverty, corruption, crime, plus the mostly toxic political legacy of the former Communist regime and its nasty secret police.

That heady brew burst forth in Skopje past week, with a brawl in parliament resulting in numerous injuries. While NATO and the EU have blamed the nationalist Right for the chaos, there are actually numerous overlapping issues at play in Macedonia, all of them contentious, including ethnic resentments, political corruption, secret police games, and haggling over forming a coalition. Nevertheless, the longstanding political paralysis in Skopje may be on the verge of breaking—in the direction of violence.

Predictably, the Kremlin has depicted the chaos as—you guessed it—a Western plot against Orthodox Slavs. There is real danger that Macedonia could come unglued if this crisis is not brought to a heel quickly. It wouldn’t take much clandestine Russian prodding to turn Skopje’s brawling into actual war. That was narrowly averted back in 2001, when Russia wasn’t meddling in the country’s problems in any major way. Now, Putin may want an unpleasant distraction for NATO and the EU in Southeastern Europe, and deeply divided Macedonia would be perilously easy to push over the edge.

It bears noting that Macedonia collapsing into ethnic war is the region’s longstanding nightmare scenario. Any sustained violence between Slavs and Albanians might rapidly drag in neighboring states like Albania and Serbia. If that happens, Bulgaria and Greece—both NATO countries which have a special interest in Macedonian matters—may not be far behind. Ethnic squabbles in that tiny Balkan country could devolve into a regional war with alarming ease.

It is therefore in the West’s interest to tamp down festering crises in the Balkans—above all in Macedonia—before they get out of hand. That will require keeping Russian malfeasance in the region to a tolerable level, yet it will also require NATO and the EU to confront the reality that the solutions they imposed on the former Yugoslavia in the 1990s are no longer functioning. Indeed, they constitute a big part of the problems imperiling Southeastern Europe today.

John Schindler is a security expert and former National Security Agency analyst and counterintelligence officer. A specialist in espionage and terrorism, he’s also been a Navy officer and a War College professor. He’s published four books and is on Twitter at @20committee.