Japan has not had a formal military since the United States wrote the country's pacifist Constitution at the end of World War II, only a self-defence force. Tokyo was happy to be the joey in the American kangaroo's pouch. Thus protected by treaty, it could afford to limit its defence spending to 1 per cent of gross domestic product.

Times are changing though. Americans are getting weary of meddling in too many overseas conflicts and also are taking a knife to their defence budgets. Washington wants its allies to pay more of their own bills, and help one another.

Japanese pride was dented after China overtook Japan in 2010 as the world's No. 2 economy. It still is the second biggest contributor to the United Nations but is denied a seat on the Security Council. Its wheezing economy gains by developing its arms industry, which has first-rate technology. Meanwhile, the decades have erased guilt about Japan's role in the Great War while China has grown to be an assertive power.

Toss in Prime Minister Shinzo Abe, who, like China's President Xi Jinping, has his own glory dreams and you know why Japan is re-interpreting its Constitution to permit its military to deploy overseas in support of an ally, even if there is no direct threat to Japan.

Mr Abe's move to turn Japan into a "normal nation" has implications for South-east Asia. He has signalled deep interest in the region, through which most of his country's trade and oil supply passes, visiting all 10 Asean states in his first year since returning to office.

Defence policy has moved in lock-step: Japan now has an "extensive strategic partnership" with Vietnam, an "enhanced strategic partnership" with Malaysia and recently held naval exercises with the Philippines in the South China Sea. It does regular naval drills with India and will soon make its first major arms export to that country. Not surprisingly, all four have territorial disputes with China.

Asean is becoming a yam between many boulders.