As India is observing a day of national mourning as a sign of respect towards former Japanese PM Shinzo Abe, let's have a look at how the relations between the two countries flourished under him.

The QUAD: Abe delivered a speech "Confluence of the Two Seas" in 2006 that laid the foundation of 'Indo-Pacific' concept.

• He argued that the Indian and the Pacific Ocean must not be seen as two different geopolitical arenas but instead as a single integrated geopolitical theatre.

• Abe returned to office in 2012 and backed his vision of a security diamond with a will to revive the QUAD.

• Even after stepping down, Abe was continuing to work on strengthening the QUAD. He attached Indo-Pacific to strengthening the bilateral relationship between India and Japan.

Infrastructure: Under his watch, Japan invested heavily in Indian infrastructure, including in the sensitive parts of India's North East.

• The bullet train project is the largest with Japan providing around 81 per cent of the funding for the project in the form of a loan worth $12 billion, at a cost of 0.1 per cent, for a 50-year period including a 15-year moratorium.

• It became the first foreign country to be allowed to invest in the Andaman and Nicobar Islands and is assisting India in developing civilian and strategic infrastructure there.

• JICA signed an agreement with India to provide $610 million for the North-East Road Network Connectivity Improvement Project. India-Japan Coordination Forum for Development of North East was set to focus on strategic infrastructure, electricity and disaster management.

Defence: The two countries have shared concerns about China, with which both have major territorial disputes.

• Under Abe, Japan became a permanent member of the Malabar Exercise between India and the US in 2015, and is also engaged with India and Australia in a trilateral dialogue.

• The two countries advanced their cooperation in the maritime security domain, signed agreements on defence technology transfers and agreed to share classified military information.

• India also improved security partnership with Australia, arguably Japan’s second most important strategic partner. Australia and India held their first ever bilateral naval exercises in 2015.