India’s Prime Minister Narendra Modi performs yoga with others to mark the International Day of Yoga, in New Delhi, India, June 21, 2015. Photo by Adnan Abidi courtesy of Reuters

KOLKATA (Reuters) An ascendant Hindu nationalist group wants minority Muslims and Christians to accept that India is a nation of Hindus, and is pushing some of them to convert.

An election in the volatile state of West Bengal has become a prime target in its game plan.

The group’s strategy: To spread its Hindu-first ideology to all corners of India by propelling the ruling party of Prime Minister Narendra Modi to power in as many states as possible. The Rashtriya Swayamsevak Sangh (RSS) provided the foot soldiers in last year’s landslide general election victory by Modi, who joined the movement in his youth.

Winning states like West Bengal, outside the ruling party’s traditional strongholds, would give Modi greater control over the upper house of parliament, which would put him in a better position to push through key policies. The game plan of Modi’s Bharatiya Janata Party (BJP), which is in the minority in the upper house, is to govern 20 of India’s 31 regional legislative assemblies over the next four years, top party sources said. It currently controls or shares power in 11.

Interviews with more than two dozen RSS and BJP officials and rare access to closed RSS meetings reveal a two-stage strategy – electoral victory at the national level, which has been achieved in the lower house of parliament, followed by similar success at the state level.

“We would want the BJP to win all the state elections because only then can significant social, political and cultural changes take place in this country,” RSS Joint General Secretary Dattatreya Hosabale told Reuters. “The 2014 election victory should be seen as the starting point of a long term mission.

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What is unfolding is a battle for the soul of India. Since independence in 1947, Indian politics has been dominated by the Congress party and its leftist offshoots. They have espoused a secular, multi-faith vision of the nation. Hindus are the majority, but roughly 14 percent of India’s 1.2 billion people are Muslim.

The RSS was founded in 1925 as an anti-colonial organization. It promotes a fundamentally different vision that draws on a mix of Hindu legends and ancient Indian history, when the subcontinent was home to some of the world’s most advanced civilizations.

According to this narrative, India’s glory days ended after it was invaded — beginning in the 8th century — by Muslims and then Christians, who converted the Hindu inhabitants. The RSS believes that if all Indians were to acknowledge and accept that ancient Hindu identity as theirs, it would unify the country, offer the best defense against any future aggressors and head off separatist movements.

“Hindustan means land of Hindus,” RSS General Secretary Suresh “Bhaiyyaji” Joshi told Reuters, using the old Mughal Persian name for India. “So anyone living here is automatically a Hindu first.”

The RSS has been banned four times since its inception, once after a former member of the group assassinated Mahatma Gandhi in 1948. That attack came after the RSS accused Gandhi of appeasing Muslims at a time when Pakistan, an all-Muslim nation, was being carved out of India. The ban was later lifted in the absence of any evidence the group planned the attack.

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Until a few years ago, the RSS had focused on achieving its vision of a Hindu nation from outside the electoral realm. RSS volunteers would meet weekly at thousands of shakhas, or branches, around the country to talk about Hinduism and civic duty, and practice martial exercises and discipline. Those interested in electoral politics traditionally migrated to the BJP and its predecessor, Jan Sangh, which shared much of the RSS’ ideology.

That changed in July 2013. At a meeting in Amravati in the western state of Maharashtra, RSS leaders decided it was time for the group to start using its network to more systematically help the BJP come to power, according to Ramapada Pal, the RSS chief preacher for West Bengal and Odisha states. His account was confirmed by several other RSS and BJP leaders who attended the meeting.

One speaker helped convince those resisting the change by acknowledging that politics was dirty, like a “toilet,” but that it was for the RSS to clean up the mess, Pal said.

After the Amravati meeting, BJP president Shah enlisted an army of RSS volunteers in Uttar Pradesh, India’s most populous state, to campaign for the BJP in the federal elections of 2014.

The BJP won 71 parliamentary seats in Uttar Pradesh – a record for the party.

Now, the RSS and BJP are hoping to replicate the Uttar Pradesh playbook in state elections. Bihar, an impoverished eastern state that is currently governed by a coalition of BJP rivals, started voting in a state election on Monday. RSS volunteers have run a grassroots campaign in the state.

But the acid test for the RSS-BJP alliance will be next year’s elections in West Bengal, a state where the BJP is traditionally weak and which for decades was ruled by an alliance headed by Communist parties.

Communal violence is never far from the surface in places like West Bengal. Some of the worst religious rioting in Indian history followed the partitioning of British India into predominantly Hindu West Bengal and Muslim East Bengal, which in 1971 became the new country of Bangladesh. More recently, Hindu-Muslim riots erupted in West Bengal in 2007, 2010 and 2013.

In the months after Modi’s victory, leaders of hardline Hindu groups launched a drive to have India officially declared a nation of Hindus. They also stepped up a campaign against what they called “Love Jihad” – a term used to describe what they claimed was an Islamist strategy to convert Hindu women through seduction, marriage and money. And they began a push to convert Muslims and Christians to Hinduism, through a purification ritual called “ghar vapsi”, or “homecoming”, a concept central to the RSS since its founding.

Cow slaughter, another touchstone issue for the RSS and the source of many lethal riots, has again shaken India this month after a Muslim man was lynched near Delhi on suspicion he had killed a cow, an animal holy to many Hindus. His death at the hands of a Hindu mob was deemed “an accident” by Modi’s culture minister.

Modi has been criticized for giving hardliners a free rein, but their zeal has also caused him headaches.

After meeting the prime minister in January in New Delhi, U.S. President Barack Obama urged India not to stray from its constitutional commitment to allow people to freely “profess, practice and propagate” religion.

By Rupam Jain Nair and Frank Jack Daniel; Editing by Bill Tarrant and Peter Hirschberg