Japan, the only nation to have suffered nuclear attacks, has a self-imposed ban against owning nuclear weapons and relies on the nuclear umbrella of the United States, its close security ally. Operating under a pacifist constitution, the SDF does not own attack-oriented aircraft carriers or long-range bombers.

BUDGETARY LIMITS

Japan’s defence budget fell for the 10th straight year to 4.65 trillion yen ($59 billion) for the current fiscal year ending in March 2013, reflecting the constraints of Japan’s huge public debt, which is the worst among industrialized nations at twice the size of its annual economic output.

In contrast, the defence budget of China nearly doubled to 650 billion yuan ($102 billion) over the past five years.

STRETCHING CONSTITUTIONAL CONSTRAINTS

Article 9 of Japan’s 1947 Constitution renounces the right to wage war to resolve international disputes and bans the maintenance of a military.

But the article has been stretched not only to permit the maintenance of armed forces for self-defence, but to allow overseas military activities -- including deployment in 2004 of troops on a non-combat mission to Iraq.