When Azerbaijan went to war this week with Armenia over the breakaway territory of Nagorno-Karabakh, it might have appeared as an obscure conflict with little resonance outside the south Caucasus.

Until you turned to the Twitter account of one of the most famous people in the world, Kim Kardashian. Or that of her husband, Kanye West. Metal fans might have seen tweets about the war from Serj Tankian, the lead singer of System of a Down. If you missed those, there were also posts by Alexis Ohanian Sr, the founder of Reddit and husband of Serena Williams, and former Arsenal footballer Henrikh Mkhitaryan.

The prominent names were among members of the Armenian diaspora who sprang into action when the conflict erupted on Sunday morning, publicising Armenia’s cause in its long-running dispute with Azerbaijan over Nagorno-Karabakh, a territory that is legally Azeri but has been run by a self-declared government of ethnic Armenians since 1994.

Armenia has a population of about 3 million people. But its diaspora, concentrated in the US, with significant hubs in Lebanon, Australia, France and Russia, extends to at least double that size. Woven deeply into its culture are the events of 1915, when historians estimate as many as 1.5 million Armenians were killed by Ottoman Turks in a campaign widely consider by scholars (and stridently denied by Turkey) to be genocidal.

Generations of displacement has nurtured a resilient national identity-in-exile, and a powerful political machine to match. Its heart is southern California, with an Armenian-origin population of at least 500,000 people, according to one estimate, though Armenian advocacy groups say their numbers are twice as many in Los Angeles county alone.

“In a city like LA … you have Armenian schools, Armenian businesses, Armenian churches,” said Alex Galitsky, from the LA-based Armenian National Committee of America’s western region. “Someone could grow up living in LA and never be exposed to anything other than Armenian culture.”

“In the consciousness of the Armenian diaspora, the reason for our community’s existence in these places outside of Armenia is directly a result of the genocide,” Galitsky added.

Since the outbreak of fighting on Sunday – which many analysts say appears to have been instigated by Azerbaijan, albeit after months of tensions being ratcheted up on both sides – Armenian lobby groups have been holding protests, asking Armenian-Americans to lobby their representatives and briefing congresspeople and the media.

Azerbaijan sees the conflict as an effort to reclaim land illegally occupied by Armenian separatists, who forcibly displaced about 7% of its population – roughly 600,000 people – when they took control of Nagorno-Karabakh and surrounding areas during a 1990s war.

For Armenians, the involvement of Turkey in backing Azerbaijan has confirmed their view that it is an existential conflict. “We view this as a continuation of the genocide,” Galitsky said.

In recent years, the Armenian government has stepped up efforts to persuade the diaspora to resettle in the country. Birthright Armenia – which is modelled on a similar Israeli organisation – has since 2003 helped to pay for young diaspora Armenians to live and volunteer in the country.

About 50,000 diaspora Armenians have moved to the country since 1991, according to Repat Armenia, an NGO that assists with the resettlement. Those numbers have surged by 15,000 since a peaceful revolution in 2018, according to one estimate.

Since the start of the Syrian civil war, about 22,000 Syrians of Armenian origin have also resettled in the south Caucasus, according to the Migration Service of Armenia. Many have made their new homes in Nagorno-Karabakh – a trend considered highly provocative and an “illegal settlement policy” by Azerbaijan.

Some of the Armenians who return to the Caucasus do more than settle. During the 1990s war with Azerbaijan, many formed ragtag fighting units that took an active part in the war. One of those who returned wasMonte Melkonian, who was born in California and learned Armenian only as an adult, but died in the battle for Nagorno-Karabakh in 1993. Melkonian is considered a national hero.

The fighting this week is the latest spur for many young diaspora Armenians to return. “As diaspora everyone feels the same: we have been waiting for this moment our whole lives,” said George Arbajian, a law student born and raised Beirut, Lebanon, who is leaving for the Armenian capital, Yerevan, next week.

“The idea of fighting for the motherland is very romantic and we are raised with that,” he said. “If the perpetrators of genocide are back we have to go back to the battle field, we don’t have a choice.

“When I say that I mean that could be picking up a gun, helping with logistics, doing aid or water deliveries to [Nagorno-Karabakh’s main city] Stepanakert. I don’t want to say that I’m going to go and pick up a gun and go to the frontline. But I am definitely a step closer to it. I know a lot of people who are doing that.”

Galitsky discusses the phenomenon of returning to take up arms carefully – inciting people to join foreign militias is a serious offence in many jurisdictions. But he acknowledges it happens in Armenian diaspora communities in France and the US, too.

“It’s a tricky situation because of the legal issues around it, but we’ve seen diaspora brigades in the past, especially from Syria, Lebanon and France mobilise and go to Armenia. I’ve anecdotally heard reports of people from our communities here returning [to Armenia].”

“It is not surprising” he continued. “I think a lot of people see themselves as bearing some responsibility for the defence of our nation.”