India and Canada are embroiled in their biggest diplomatic spat in living memory, resulting in tit-for-tat moves that saw Canada expel the station chief of the Research and Analysis Wing, or RAW, the Indian intelligence agency. Within hours, the Indian government responded in kind and expelled the Canadian intelligence agency's station chief in India.

"The concerned diplomat has been asked to leave India within the next five days," said a press release issued by India's Ministry of External Affairs (MEA) on Monday (September 18), adding, "The decision reflects the Government of India's growing concern at the interference of Canadian diplomats in our internal matters and their involvement in anti-India activities."

The language of the press release is not what you usually see between friendly nations. And it has kept getting worse. But how did it all come to this? And could it have been avoided?

Roots of the conflict

The row exploded into a full-blown international crisis on Monday, when Canadian Prime Minister Justin Trudeau told Parliament that Canadian security agencies were "actively pursuing credible allegations of a potential link between agents of the government of India and (Hardeep Singh) Nijjar's death".

Hardeep Singh Nijjar, 45, was shot dead outside a Sikh temple on June 18 in Surrey, a suburb of Vancouver with a large Sikh population (Canada is home to the world's largest population of Sikhs outside the Indian state of Punjab). Nijjar was known as an ardent supporter of a separate Sikh homeland, Khalistan, to be carved out of Punjab, and was designated as a "terrorist" by India in July 2020. The Khalistan Tiger Force chief was the fourth Khalistani separatist to be killed on foreign soil in 2023, and fuelled speculation within India itself that RAW was mounting a secret operation to eliminate such elements in the Indian diaspora.

Trudeau said any involvement of a foreign government in the killing of a Canadian citizen was "an unacceptable violation of our sovereignty", adding he had raised the murder with Indian Prime Minister Narendra Modi on the sidelines of the G20 summit in New Delhi.

Analysts are of the view that Trudeau's decision to go public with the accusation in the way that he did was driven at least partly by the torrid time he endured in New Delhi during the G20 summit, held September 9-10. After the summit was over, Trudeau remained stranded in Delhi for two days as his aircraft experienced technical difficulties. By all accounts, he spent those two days holed up in his room at the Lalit Hotel with his son, who was travelling with him.

If the Canadian leader spent those two days checking out the Indian media, he would have seen they were full of reports essentially trolling him, on him being rebuked by his counterpart Narendra Modi during the summit itself. The two prime ministers did not hold a formal bilateral meeting at the summit, but in a brief conversation on the sidelines, Trudeau said the pair discussed foreign interference and "respect for the rule of law."

Meanwhile the Indian MEA in a handout said Modi conveyed "strong concerns about continuing anti-India activities of extremist elements in Canada. They are promoting secessionism and inciting violence against Indian diplomats, damaging diplomatic premises, and threatening the Indian community in Canada and their places of worship."

"The nexus of such forces with organised crime, drug syndicates and human trafficking should be a concern for Canada as well," it added.

The Khalistan movement in Canada

Asked about India's concerns over the increasing activities of Khalistani elements in Canada, Trudeau said at a press conference that his country "will always defend freedom of peaceful protest, freedom of conscience, and freedom of speech" but at the same time asserted that it will always prevent violence and push back against hatred. This did not go down well with his hosts, and drove much of the criticism in the media.

For Trudeau, it must have felt like groundhog day all over again. He endured an even more torturous trip in 2018, when he had to wait till the fifth day of a six-day state visit to gain an audience with Modi. Speaking to CNN at the time, Dhruva Jaishankar, a fellow at Delhi-based think tank Brookings India, said that Modi's apparent cold shouldering of Trudeau was significant.

"This is quite clearly a strong signal that India is very unhappy with the Trudeau government for its approach to this (Khalistani separatist) issue," said Jaishankar.

What Canada would describe as 'political activism' or protests on its soil by the large Sikh population in the country (numbering 770,000 or 2.1 percent of the population in the latest census) has been a flashpoint between Delhi and Ottawa throughout Trudeau's time in office. After appointing four Sikhs to his first cabinet in 2015, Trudeau boasted about having more Sikh ministers than Modi, who was elected a year earlier. Soon however, attention turned to his perceived proximity to individuals sympathetic to the Khalistani cause, straining bilateral relations.

Defence Minister Harjit Singh Sajjan's ties to the movement received particular focus. Today he remains part of Trudeau's cabinet, serving as minister of international development. The current Trudeau administration, following the elections in 2019, is a minority government dependent on the New Democratic Party for its majority in parliament. The NDP is headed by Jagmeet Singh, described in the Indian media as "an arch-Khalistani separatist". In the wake of Trudeau's speech in parliament on Monday, Singh has vowed to hold Narendra Modi "accountable".

In a sharply-worded rebuttal on Tuesday, the Indian MEA said the allegations made by Trudeau were "absurd and motivated". It went on to add: "Such unsubstantiated allegations seek to shift the focus from Khalistani terrorists and extremists, who have been provided shelter in Canada and continue to threaten India's sovereignty and territorial integrity. The inaction of the Canadian Government on this matter has been a long-standing and continuing concern."

How serious is the threat?

That 'long-standing' concern stretches back to at least 1982, when the Indian government asked for the extradition of a Khalistani militant, Talwinder Parmar, wanted for the murder of police officers in Punjab. But the Canadian government, then led by Justin's father Pierre Trudeau, refused. Stunningly, Parmar, who was the head of Babbar Khalsa, a Khalistani separatist group, would go on to bomb an Air India plane, the Kanishka, in 1985, which blew up midair off the coast of Ireland, killing all 329 people aboard.

A commission of inquiry set up under Justice John Major gave a report in 2010, which squarely blamed Canadian police and intelligence for grave negligence. Canadian authorities should have known that Air India Flight 182 was a terrorism target, Major said, adding that the failure of the Royal Canadian Mounted Police (RCMP, or 'the Mounties') and Canada's spy agency Canadian Security and Intelligence Services (CSIS) to prevent the tragedy was "inexcusable."

Some of the evidence presented in the inquiry rings eerily similar to some of the rhetoric Nijjar and his associates were reportedly engaging in recently. Parmar, who was killed by Indian police in 1992 after sneaking into the country, told his followers in 1984 that "Indian planes will fall from the sky." That same year, one of his associates, Ajaib Singh Bagri, told the founding convention of the World Sikh Organization, another entity designated as 'terrorist' by India: "Until we kill 50,000 Hindus, we will not rest!"

It was the same year that Indian forces stormed the Golden Temple, Sikhism's holiest shrine, in Amritsar to flush out separatists who had taken refuge there. The operation killed around 400 people, according to official figures, but Sikh groups say thousands were killed. It was part of a crackdown on an armed insurgency that lasted around a decade. The dead included Sikh militant leader Jarnail Singh Bhindranwale, whom the Indian government accused of leading the armed insurgency.

On Oct. 31, 1984, Prime Minister Indira Gandhi, who ordered the raid on the Golden Temple, was assassinated by two of her bodyguards, who were Sikh. Her death triggered a series of anti-Sikh riots, in which Hindu mobs went from house to house across northern India, particularly New Delhi, pulling Sikhs from their homes, hacking many to death and burning others alive.

There is no active insurgency in Punjab today, but the Khalistan movement still has some supporters in the state, as well as in the sizable Sikh diaspora beyond India. Canadian journalist Terry Milewski, who has tracked the movement since the Air India bombing, told a broadcaster in his country recently that the Khalistan movement had died down everywhere in the world, "except in Canada." The Indian government has warned repeatedly over the years that Sikh separatists were trying to make a comeback.

India has also been asking countries such as Canada, Australia and the United Kingdom to take legal action against Khalistan activists. Earlier this year, Sikh protesters pulled down the Indian flag at the country's high commission in London and smashed the building's window in a show of anger against the move to arrest Amritpal Singh, a 30-year-old separatist leader who had revived calls for Khalistan and stirred fears of violence in Punjab.

Protesters also smashed windows at the Indian consulate in San Francisco, setting fire to it briefly, and skirmished with embassy workers. The Indian government also accused Khalistan supporters in Canada of vandalising Hindu temples with "anti-India" graffiti and of attacking the offices of the Indian High Commission in Ottawa during a protest in March.

For its part, the Canadian government has consistently maintained that their Indian counterparts had failed to present them with the requisite evidence to take action against these elements, many of whom are now Canadian citizens.

Against this background, it was seen as almost a matter of time before India started taking matters into its own hands, as part of a more assertive, muscular foreign policy under Modi. Of the four Khalistani leaders killed in 2023, two were gunned down in Pakistan, which India considers an enemy state. In May, Avtar Singh Khanda, who allegedly planned the attack on the Indian High Commission in London, died in the UK. Although he was suspected to have been poisoned, UK authorities said he was suffering from blood cancer. Understandably, none of these deaths had the potential to generate the kind of backlash as the murder of a Canadian citizen on Canadian soil, by operatives possibly working for a friendly state.

Trudeau on Tuesday said Canada is not trying to provoke India by suggesting it was linked to the murder of Nijjar, but wants New Delhi to address the issue properly. He told reporters that the case had far-reaching consequences in international law.

"The government of India needs to take this matter with the utmost seriousness. We are doing that; we are not looking to provoke or escalate," he said.

The two countries, meanwhile, issued travel advisories for their respective citizens, with Indians warned by their government to watch out for "politically-condoned hate crimes" in Canada.

Nijjar was shot as he was leaving the parking lot of the Sikh temple where he served as president in British Columbia. He suffered multiple gunshot wounds and died at the scene.

After the killing, a lawyer and spokesperson for Sikhs For Justice, Gurpatwant Singh Pannun, said he had spoken to Nijjar by phone the day before he was killed and that Nijjar had told him that Canadian intelligence had warned him that his life was at risk.

Notably Pannun too is designated as a terrorist by the Indian government, and in the wake of Nijjar's killing, there was talk in the Indian media of him being targeted next, as India's 'top priority'. He himself has been issuing dire threats to 'Indo-Hindus' to leave Canada

The entire affair has also caused talks over a trade deal between the two nations to break down. As things stand, Trudeau will have to come forward and present what evidence he has, if India continues to be dismissive of the allegations he brought. Yet that may only serve to escalate the situation further. Ultimately, he may have to make a very difficult choice between preserving his own credibility, or preserving relations with India.

Alternatively, there is a view within India that the Khalistan movement, in its present state, does not merit the kind of attention it has received from the Modi government.

Hartosh Singh Bal, executive editor of The Caravan, told Al Jazeera "The Khalistan movement has a long history and during the 1980s, there was a violent military movement on Indian soil. But ever since - at least in India, in the state of Punjab, where the Sikhs are the majority - the Khalistan movement has been virtually non-existent, enjoys no political support and goes up and down depending on the attention the Indian government pays to it."

He went on to add that the kind of activism the movement's adherents abroad were involved in "could have ideally been easily ignored".

Now however, the entire issue has reached a juncture from where it may well be impossible to ignore. And the fallout will be monitored closely in the days ahead around the world.