It was quite a demonstration when hundreds of thousands of practitioners worldwide, along with over 36,000 Indians in Delhi's Rajpath, performed yoga all together on Sunday, celebrating the first International Yoga Day.

The event, which was designated by the UN earlier this year at Indian Prime Minister Narendra Modi's recommendation, has set two new records, for holding the largest yoga demonstration in a day, and for "the participation of the largest number of nationalities in a single yoga event."

As the homeland of yoga, one of the most famous parts of the country's cultural heritage, it is natural for India to strive to improve the popularity of this activity. This time, Modi is obviously attempting to play the soft power card by promoting yoga in such a large-scale exercise, in order to showcase India's will to become a global power, boost the nation's global image, and the most important of all, to unite Indian people and promote nationalism.

India was not really a united country historically, given the long-term diversity and divisions of its people even in the British days. Indian citizens therefore do not have much national consciousness. Modi has realized that this can be a great opportunity to strengthen India's national spirit and enhance national cohesion by promoting yoga exercises.

But the bitter truth is that it will prove to be hard for things to go exactly as he wished.

As a diverse country, India is the home of over 800 million Hindus, nearly 200 million Muslims, approximately 9 million Buddhists, and other minority ethnic groups. In certain remote regions of the country, there are disturbances caused by anti-government armed forces from time to time. The battle between religious sectarianism and secularism lingers, with the opposition Congress Party of India wanting to embrace secularism, and separate religion from politics. But the BJP, with its Hindu nationalist ideology, will never agree with that.

A glimpse at all these issues highlights the challenges which Modi will have to confront in terms of uniting the diverse nation.

International Yoga Day is a clear example.

Not every Indian is a fan of it. Some members of the Muslim community are unhappy with this promotion of yoga, arguing that the practice of the sun salutation, a series of basic poses in yoga, goes against the monotheistic nature of Islam. Plus, they believe the chanting of the word "Om" while doing yoga is closely connected to the Hindu religion.

BJP spokesperson Nalin Kohli has claimed that "there is no religious angle to this at all," but it was obvious from the start that popularizing a Hindu-associated practice would bring up the religious contradictions and accusations of sectarian bias that have always haunted Modi.

Modi has been laying out loud, clear and cheerful slogans since assuming office, including making India a superpower by 2020. But India's industrial strength still lies over in software. Hence, Modi's efforts to promote the country's soft power should be coordinated with efforts in other hard power areas.

But India's manufacturing has not achieved the strength the country hopes for. Many high-tech projects are still dependent on foreign technology, and the country's industry remains largely orientated toward the lower end of the industrial chain.

The obstacle of solving this problem still lies in the difficulty of uniting the nation. With India's land reform, education and population problems still pending, it remains hard for the central government, local administrations and citizens to reach a consensus over a large number of issues.

Modi will keep facing resistance in the days to come. He is making a good effort, but the effects are worrying.