Courtesy of Public Relations Office, Indian Navy

For two days last month, ships from the Indian and Japanese naval forces held joint military exercises in waters off Tokyo. By military standards, the exercises were small in scale. But they were heavy with symbolism and brought to light another facet of the growing relationship between the two countries — defense.

Their growing collaboration is expected to lead to tighter cooperation in one of the world’s most increasingly important regions, the Indian Ocean. And given the shadow cast by the regional giant that separates the countries, it is a relationship that many observers feel is long overdue. (Read more about Japan and India’s growing economic ties.)

Such joint exercises might be standard practice in international military-to-military exchanges, but with growing regional tensions — like in the South China Sea, located between India and Japan — they take on a more complex meaning.

“If you look at it through a containment of China prism, it makes sense. Everybody is very worried about China,” said Rahul Bedi, a regional defense expert — particularly the Indian Navy, as China flexes its muscle in the Indian Ocean.

According to an Indian Navy spokesman, Commander PVS Satish, the ships involved covered basic exercises aimed at simply “understanding each other’s operational and communication procedures.” Around 1,400 sailors from four ships were involved, including the missile destroyer I.N.S. Rana and the frigate I.N.S. Shivalik.

The joint exercises were part of official commemorations of 60 years of diplomatic ties between the two countries; there has also been a flurry of high-level visits back and forth, including a trip to India last November by Prime Minister Yoshihiko Noda of Japan. There is a lot to celebrate, given that just 15 years ago, relations hit a low point when Japan deeply objected to India’s testing of nuclear weapons.

While they could be seen as simply an attempt to build practical naval experience with each other, the exercises could also be taken as part of efforts to boost India’s naval power and project its influence beyond the Indian Ocean.

“This is part of a wider ambition to show the flag regularly east of the Strait of Malacca, now that India is becoming an Indo-Pacific nation and not solely an Indian Ocean power,” said Rory Medcalf, director of the International Security Program at the Lowy Institute, an Australian foreign policy think tank.

“At sea, both have serious navies. Japan’s may be more advanced, for instance, with its strong submarine fleet, but India has the benefit of long experience in the Indian Ocean,” he said.

There are growing fears that the Indian Ocean region might become a battleground in any future regional conflicts. Home to vital shipping routes as well as piracy issues, it is bordered by Australia, Asia and Africa, with India and China at its core. Beijing has been working hard to build up its naval capacities here, including interests in ports in Sri Lanka, Pakistan and Bangladesh — something that has India deeply concerned.

In addition, the South China Sea is particularly geostrategically important, as it is critical to global shipping routes and has enormous potential oil and natural gas reserves. But it is also pockmarked by a handful of worrying territorial disputes.

Still, it is important to note that India is striving to at least maintain what maritime ties it has with China. The ships that took part in the Tokyo exercises stopped in at Shanghai on their way back to India, in the first naval visit by Indian ships to China in six years.

“The ships’ visit is a high point of defense exchanges this year, as it is designated by both the countries as a year of friendship and cooperation,” S. Jaishankar, India’s ambassador to China, told the Press Trust of India news agency.

In addition, ships from China, Japan and India are all involved in guarding the strategically important Gulf of Aden, in Yemen, from piracy.

While China’s neighbors might be keen to curtail its maritime ambitions, they are also trying to engage with the country and retain good relations. Regional powers are swimming around each other, cautiously and nervously, jockeying to assert their own strength but trying to avoid the kind of sea-based conflict that many observers fear is looming.

“It makes sense for them to cooperate against transnational maritime threats like piracy,” said Mr. Medcalf. “The big challenge for all these countries will be to figure out a way of working with China in the Indian Ocean.”