Until the autumn of 2020, a boutique part of the travel industry offered tour packages to a place that didn’t exist. Nagorny Karabakh – ‘the Black Garden’ – covers an area of the southern Caucasus around a quarter of the size of Wales. It’s a hard-to-reach backwater of verdant mountains crisscrossed with rivers that descend to rolling plains. Historic monuments punctuate its natural beauty: churches, mosques and ancient sites and cities perched on jagged peaks.

The draw for the adventure tourists was the scars of its recent past. A war between Azerbaijan and Armenia raged in Karabakh from 1988 to 1993 and, by the end of it, large parts were abandoned and land mined. It fell under the control of an ethnic Armenian administration but remained internationally recognised as the territory of Azerbaijan, and for nearly three decades, according to the political map, Karabakh was a country in name only. Even its name was disputed: Nagorny Karabakh was the name of the Soviet era oblast, known as Qarabag to the Azeris and Artsakh to the Armenians. From 1993 until 2023, the only way to enter the unrecognised Republic of Artsakh was from Armenia proper, via a single road that cut through Azerbaijan. A tour company could arrange the permission from the authorities in Stepanakert, its capital, although they advised you to keep the stamp off your passport: anyone who visited occupied Karabakh was automatically banned from ever entering Azerbaijan. Some 150,000 ethnic Armenians continued to live in the territory, under a quasi-government that issued them passports that were recognised almost nowhere. Men were conscripted into the Artsakh Defence Forces, a local paramilitary organisation, for two years from the age of 18. Around 700,000 Azeris fled Karabakh during the war, and then scraped out lives as refugees in the slums of Azerbaijan’s cities. While Karabakh’s Armenians lived mostly up in the mountains, the Azeris’ abandoned homes down on the plains became ghost towns and villages, marketed as dark tourist attractions complete with rusting Soviet tanks and bullet-riddled buildings.

Europe’s hinterlands are littered with grey zones like Nagorny Karabakh: patches of territory torn between rival nation states and their conflicting understandings of the past and future. They are fascinating and kitsch – and combustible. In the southwestern corner of the old Soviet Union, a thousand miles from Nagorny Karabakh, Moldova, another emerging post-Soviet state, also collapsed into war in the early 1990s. Its part to the east of the river Dniester – a region known as Transnistria – broke away to form a separatist state that kept its links with the Russian motherland and, until 2017, its branch of the KGB.

To enter Transnistria in 2019, I boarded a marshutka, a public minibus, in the Moldovan capital Chisinau and travelled for an hour along roads that got progressively bumpier the further we got from the city. Eventually we reached the de factor border, just before the Dniester, and filed into an office where a surly Transnistrian border guard made us fill in visa forms. After that, we drove into a time warp. In Bendery, the first Transnistrian town, the routes at the bus station are still displayed on Soviet era maps, and other fragments of the past are littered everywhere. The local tourism board had recently realised the pulling power of Transnistria’s Lenin statues and its crumbling Soviet factories adorned with modernist murals. In the gift shop of its information centre it sold mugs featuring Marx partying with Trotsky and Lenin, and fridge magnets ‘from the place that doesn’t exist’.

In the Balkans, grey zones emerged from the peace agreements that carved Yugoslavia into new nation states after the wars of the 1990s. The Dayton Accords halted the bloodshed in Bosnia by dividing the country into administrative districts according to its three ethnicities: Bosniak Muslim, Serb and Croat. The Serb part, Republika Srpska, has been led almost since the start by Milorad Dodik, a belligerent nationalist who has courted Putin and Steve Bannon, and has recently started threatening to fully cede from federal Bosnia. Meanwhile, Kosovo, a majority-Albanian Muslim part of Yugoslavia, fought a war against Slobodan Milosevic’s Serbia at the turn of the millennium, was governed as a UN and then EU protectorate, and finally declared independence in 2008. Serbs see Kosovo as an indivisible part of Serbia, and Belgrade has lobbied hard to dissuade other countries with ethnic breakaway problems from recognising it; presently, 102 of the 193 UN member states and 22 out of 27 in the EU recognise Kosovo. Its northern part, which borders Serbia, is home to a majority of Kosovan Serbs and is run as a quasi-state, with its main political party linked directly to the halls of power in Belgrade and stirring up trouble on its behalf. Here the tourist draw is the bridge over the river Ibar in the divided city of Mitrovica, where you walk from the Albanian south to the Serbian north in less than a minute and find a completely different language, alphabet, and set of number plates on either side.

The Britons who flock to package holidays in Ayia Napa on the Mediterranean island of Cyprus each summer are sunbathing just a few hundred metres from another grey zone. A brief, bitter war in 1974 split Cyprus in two, and so it has remained, with Greek-speakers to the south and Turkish-speakers to the north of a dividing line. Decades of UN-backed talks failed to reunite the two and their paths have diverged; the south is an EU member state, the north an entity recognised only by Turkey. They use separate currencies, and for a few years they followed different time zones, the south sticking with Greece’s clock and the north with Turkey’s an hour behind – a bonus on New Year’s Eve. Since 2003 it’s been easy for locals and most tourists to cross between the two sides; in the space of a couple of minutes and a single street you can go from the Eurozone into a place where Amazon doesn’t deliver.

These territories were long thought of as frozen conflicts: their status unsettled, but mostly benign, and posing little threat to the wider region. Over the past few years, though, things have changed. Russia and Turkey, both led by populist strongmen, are seeking to expand their spheres of influence through both hard and soft power. Their interests overlap in the Caucasus, which has, at various times, been pulled between Ottoman and Soviet occupation. Armenia kept the strongest ties to Russia at the end of the Soviet Union, while Azerbaijan rediscovered its linguistic and religious kinship with Turkey. Moscow and Ankara both project power in the Balkans, too, where Muslim populations look to Erdogan as a protector and Orthodox Christians see Russia as the mother country and Putin as their patron. Serbia’s President Aleksander Vucic, empowered by his brotherly relations with Putin, has turned up the heat on Kosovo, and over the past year there have been riots against NATO peacekeepers and a shootout involving a Kosovo Serb politician in the north of the country.

On Cyprus there’s a fuzzier battle for influence. Ankara has propped up the north since 1974 and thousands of Turkish soldiers are stationed there. Erdogan has extended his influence in recent years, at the same time as he has played risky brinkmanship with Greek and Cypriot warships in the Eastern Med. Yet Cyprus is no cleaner to the south of the divide: the Greek Cypriot government began selling passports a decade ago through a citizenship by investment scheme, cooked up to help its banking sector recover from the 2012 banking crisis. Anyone spending two million euros on property in Cyprus also got a passport – an EU passport – thrown in. Russians, including sanctioned oligarchs, were the biggest buyers. The port city of Limassol, once a British expat hub, became a Russian enclave with fur shops and Slavic supermarkets. In 2015 the Cypriot government allowed Russian warships to use its ports as pitstops on their way to and from the Syrian war. The Ukraine war halted the trade. The Republic of Cyprus must now comply with the EU’s sanctions on Russia, has halted passport sales and is now refusing Russian warships to dock in its port. Luckily for anyone in need of a place to park money, northern Cyprus has started its own property investment model, offering no-questions-asked residency permits to anyone investing in property. Thousands of Russians have bought apartments in the new developments that have mushroomed in the north over the past two years.

Nagorny Karabakh was the first frozen conflict to thaw. Azerbaijan never forgot or forgave, and in the years after its defeat in Karabakh it grew rich off Caspian Sea gas and forged arms deals with Israel and Turkey. In the autumn of 2020, it launched a surprise offensive using Turkish-made drones and Syrian mercenaries, and quickly overwhelmed Armenian forces. Within 44 days Azerbaijan had seized back the parts of Karabakh previously inhabited by ethnic Azeris. Its army stopped just outside Stepanakert and the two sides signed a peace deal, with Russian and Turkish peacekeepers as guarantors.

After Russia invaded Ukraine in 2022, the Kremlin lost interest in Karabakh. Ukraine also set Armenia on a path away from Russia; in June 2023, the Armenian prime minister Nikol Pashinyan said his country did not support the Kremlin’s war, and that its position had left it vulnerable. Azerbaijan spotted an opening. In January 2023 it began blockading the Lachin Corridor, the sole road connecting Stepanakert to Armenia. Over the next nine months the city slowly grew hungry as food supplies halted and the electric and gas lines were cut. The Russian peacekeepers did nothing as Azerbaijan built a military checkpoint to make the blockade official. In September 2023, with Stepanakert softened, Baku launched a second military offensive. With Putin now distracted by Ukraine and no longer up for defending Armenia anyway, it took one day for Azerbaijani forces to take Stepanakert – 120,000 ethnic Armenians fled, and the entire territory was back in Azeri hands. On 1 January 2024, under the terms of an agreement signed between Baku and Samvel Shahramanyan, president of the Stepanakert administration, Nagorny Karabakh ceased to exist. Shahramanyan had signed his own republic away, and Azerbaijan had followed the first rule of war. It was all a matter of timing, Hikmet Hajiyev, a foreign policy advisor and spokesman for Azerbaijan’s President Ilham Aliyev told me, days before the start of the final offensive. Russia’s invasion of Ukraine, which after all had started a decade ago with Putin’s annexation of Crimea and the Donbas, had finally alerted the world to the danger of unresolved grey zones.

‘Now there is a growing understanding of the importance of territorial integrity,’ Hajiyev said. ‘Which country would accept illegal armed forces on its soil?’

I visited Nagorny Karabakh in November 2023, two months after Azerbaijan took back full control. I wanted to find out what happens to frozen conflicts when their status quo changes, and whether Karabakh’s experience might foreshadow what will happen in grey zones across Europe as the continent’s power balance shifts. The Azerbaijani government is in the midst of a mammoth reconstruction of Karabakh, which is planned to take until 2050. Across 4,400 square miles, it says it will rebuild the places that were abandoned, connect them back to the rest of the country through road and rail links, and move Azeris back into the region. The first task is demining: until the 2022 invasion of Ukraine, it was the most land mined place on earth. It is a painstaking, finger-light process: workers lie on their stomachs inching forwards by scraping their way with a hand trowel. As soon as ordinance is cleared from an area the diggers move in. Huge new roads are being carved across the landscape, often just a few hundred metres from working demining teams. Small patches of the new civilisation have been completed; there are villages, a conference centre and two airports, even though the region is not yet open to the general public and no chartered flights have started. Buildings so new they seem shrink-wrapped sit jarringly next to the ruins of ghost villages. Azerbaijan’s official line on Nagorny Karabakh is that Armenia’s failure to invest in the area over the past three decades is proof that it was always an imposter, and never the true owner of the land.

‘If you think that a place belongs to you then you develop and protect it,’ Umayra Taghiyeva, Azerbaijan’s deputy environment minister, told me. ‘But instead of developing we saw that they destroyed. Instead of planting trees they planted mines.’

New Nagorny Karabakh’s centrepiece will be Agdam, once a town of 30,000 people and the wealthy commercial and wine-making heart of the lowlands. Under occupation, it was Karabakh’s main tourist draw. The grand homes abandoned by Azeris fleeing the oncoming Armenian army were looted and then stripped of anything saleable; salvaged materials were hawked over the border in Iran. Finally, the buildings crumbled to the ground, then Agdam was marketed as a ‘ghost city’. The only structures kept upright were the mosaic-ed minarets of the historic mosque, which Armenian soldiers used as a lookout position over the surrounding plain. There are a few other echoes of Agdam’s past: the neoclassical façade of the old state theatre has kept the shape of some of its windows and columns, and the pomegranate trees that grace almost every front yard are still thriving. The new Agdam, a perfectly symmetrical grid of streets and segregated districts, will keep a portion of the old ruins at its centre. Already, a tourist trail has been signposted out around the city. Looming over the artefacts are huge, identikit buildings; the modern schools and apartment blocks of 2023 transplanted into a warzone preserved in aspic from 1993. This is nation state-building on fast forward; a macho application of the Lockian principle that whoever builds on the land, owns it. Former residents have begun moving back to some villages and apartment blocks across Karabakh, facsimiles of the rustic places they fled 30 years ago. Their new homes are spotless and calm: fitted out with all mod cons, all thanks to Azerbaijan’s President Aliyev, who has been making good propaganda use of the victory.

Azerbaijan’s Nagorny Karabakh is the biggest and most ambitious expression yet of a trend that I have watched building for a decade. In grey zones old and new, from northern Cyprus to occupied Crimea, there are now places that exist outside the normal reach of banking, transport and trading networks that are both trying to prove their legitimacy, and cashing in – financially and politically – from their unclear statuses. The markers are the same everywhere. The grey zones of the 2020s often come with new airports complete with passport gates and transfer areas that sit unused since no one recognises them (Russia has built one in Simferopol, the capital of Crimea, and the new Ercan Airport has just opened in north Cyprus). They are often furnished with excellent roads, all the more enjoyable to drive on because they are chronically underused. Such infrastructure projects serve as both a mark of pride for the would-be nation state, and a handy money-laundering funnel for construction companies in patron countries. Healthy cryptocurrency sectors also flourish in the cracks of the grey zones’ legislation and banking systems.

Some grey zones and their patrons are joining together; both Azerbaijan and north Cyprus are now part of the Organisation of Turkic States, a league spearheaded by Turkey, which stretches from Hungary to Kazakhstan. What keeps all the grey zones running is grievance. Often, these are justified – and if not contained, they can be exploited by actors seeking chaos, and easily explode into crisis. What comes next, if Nagorny Karabakh is an example, is unlikely to be a foundation for lasting peace. For decades, Europe’s grey zones have been quirks of history, fooling onlookers into thinking they were tame, but the region has reignited. This year looks set to be Europe’s most perilous since the end of the Cold War. As opposing forces pull again at the continent, it is the weak spots that will come apart first.

The reporting for this article was part funded by the Pulitzer Center.