Welcome to the new Great Game, where nations large and small are deepening old military ties and forging new ones across the Asia-Pacific.

It's great because the stakes are. The world's fastest growing economies are accumulating weapons and repositioning themselves like we haven't seen since the aftermath of the Cold War.

And it's a game because, unlike the Cold War, this strategic and military transformation is taking place discreetly, with defence planners tip-toeing around each other's headquarters and trying to avoid public mention of the C-word that keeps them up at night.

Tuesday we saw a new episode of the Great Game when Prime Minister Tony Abbott stood beside his Indian counterpart, Narendra Modi, and managed to outline all manner of agreements except the one which stands to transform the strategic architecture of this region.

This Framework for Security Cooperation commits Australia and India to regular maritime exercises, sharing defence technology and participating in joint military training and exercises, according to Indian official accounts.

It binds the two countries together in annual meetings of defence, foreign policy leaders and even the prime ministers of each country.

And it enmeshes each nation in each other's thinking on counter-terrorism, fighting narcotics, border protection and strategies for dealing with regional and global institutions.

Australia has even committed to supporting India's drive for a permanent seat on the UN Security Council .

This security "framework" ranks alongside Australia's deepening "quasi-alliance" with Japan, Japan's rapidly-tightening military ties with India, and the strengthening collaboration of all three countries with the United States.

It is the fourth and final cornerstone of a US-anchored democratic security "diamond", to use the old Japanese wording of an idea that rose and collapsed six years ago in the face of Chinese pressure, but has effectively been resurrected.

The reason for Mr Abbott's silence for one of his foreign policy triumphs is not that he's taking a domestic political risk.

The Opposition Leader, Bill Shorten, told Fairfax that economics should be the "load bearing pillar" of the India-Australia relationship but security ties ranked close behind.

"Our national interests are converging more broadly in the region, and heading that is security," said Mr Shorten, adding that the democratic status of both nations carried resonance with each other and across the region.

The reason for Mr Abbott's public reticence is, of course, that all this new architecture is being erected in response to a nation that dominates Australia's trade accounts like no other country has since World War II.

China is also the largest trading partner of roughly a hundred other nations, including India. But the timing is exceptionally delicate for Mr Abbott because he has spent the past few days serenading the visiting Chinese president, Xi Jinping.

It was Mr Modi who revealed the existence of this historic agreement in his joint press statement Tuesday morning. It was his Ministry of External Affairs which set out the enormous breadth and depths of mutual obligations.

And it wasn't until Mr Xi had left the mainland and landed in Tasmania Tuesday afternoon when Australian officials finally decided they had no choice but to provide at least some perfunctory official confirmation.