I first met him in 1979 when both of us were members of the Committee on Defence Planning which used to meet every fortnight under the chairmanship of then cabinet secretary Nirmal Mukherji.
Dr Singh was then secretary (economic affairs) and I was secretary (defence production). I was shifted out in March 1980. Then when he became the deputy chairman of the Planning Commission in 1986 he invited me, then director, Institute of Defence Studies and Analyses, to address the Planning Commission on national security.
Thereafter I used to run into him in the chemist's shop in New Delhi's Khan market from time to time after he returned from his assignment in the South Commission, Geneva and I had completed my visiting professorship in St John's College, Cambridge.
The first time he greeted me warmly as a brother fellow from St John's. Till 2004 whenever we met at marriage functions or in Khan Market he was always warm and pleasant.
Though I never met him during his tenure as finance minister, I was one of the supporters of his reforms programme. Subsequently once I asked him when did he change his perspective and become a convert to globalisation and the market economy, he said it was during his tenure in the South Commission.
I did not tell him how I got disillusioned with license-permit-quota Raj when I was secretary (defence production) and was in charge of defence public sector undertakings.
In June 2004 when I got discharged from the Modi Hospital and returned home, I received a call from him as prime minister enquiring about my health. A few days later I was invited for lunch. We talked about national security affairs. He had heard about my cancer and cardiac problems.
He offered that if I considered treatment abroad was necessary, the government would bear the costs. I thanked him for his generosity and said I was quite satisfied with the treatment in Delhi.
After Mani (J N) Dixit's sudden death, some in the government raised the issue whether a National Security Adviser was necessary. The PM called me and we had a couple of one-on-one discussions.
I do not know how much my views weighed with him. I was strongly in favour of continuing the office. I was also invited to take part in a discussion on Kashmir along with a number of others who knew much more about Kashmir than I did.
It was a complete surprise to me when he invited me in the autumn of 2005 and discussed with me the US strategy towards India. I had separately received a letter asking me to chair a taskforce on 'US Global Strategy; Implications and suggested response.'
In my interaction I told him that US had made a strategic decision to help building up India as one of the balancers vis-a-vis China and they are prepared to pay the price of getting us the full technology waiver on the nuclear issue. We should not let go this opportunity.
He listened as usual and did not give his own views. There were subsequent discussions -- three if I remember right on the issue. Two of them were with a number of people present while one was a private meeting.
In that meeting I advocated he should overrule some of his advisers and take a clear stand on the issue. He told me he would not do it, although he agreed with my point of view and not with his advisers.
Privately I thought he was a weak prime minister and how could he let this opportunity of liberating India from the technology thralldom to slip.
Now I know he knew much better how to get his own way.
Similarly as 2008 was passing by and there were too many concessions to the opponents of the deal, I wrote an article in The Times of India, urging that the prime minister should resign rather allow his international commitment to be dishonoured.
That would have devalued the office of the prime minister. Many people asked if I wrote that in consultation with him. I did not. I did not know at that time he had threatened to resign on the issue.
There is a school of thought which questions whether he should have made the nuclear issue such a matter of prestige when it was not on the common minimum programme.
This was an opportunity which arose out of a change in US strategy in 2005. It could not be foreseen when the UPA government assumed office. The prime minister had the intuitive sense to appreciate the opportunity and seize it.
Let us think of Pakistan which has been armed with nuclear weapons and missiles by China and has become the epicentre of terrorism using the China-provided nuclear arsenal as its shield.
Does it not make strategic sense for India to enter into strategic partnerships with all major powers which have an interest in containing Pakistani terrorism? The strategic partnership with the US was necessary to contain Pakistani terrorism which is shielded from international punitive action by Chinese nuclear proliferation to that country.
A non-aligned and isolated India would have been a vulnerable target for the nuclear-armed Pakistani jihadis to bleed it through a thousand cuts.
Dr Manmohan Singh's contribution is to end the strategic isolationism of India.
Dr Singh is certainly recognised in India and the rest of the world as a great economist. He has proved himself as a great strategist and statesman, too.
K Subrahmanyam is the doyen of India's strategic affairs experts.