The by-now defused crisis of threatened U.S.-led military strikes on Syria raised once again the difficult question of how Washington's allies should deal with U.S. wars of choice rather than necessity.
Should the United States fall under armed attack, Australia would respond spontaneously, wholeheartedly and unreservedly to fight shoulder to shoulder with kith and kin, as it should. Japan, constitutionally barred from providing combat help overseas, could still offer fulsome diplomatic support.
In an unequal alliance relationship, the same does not hold in reverse: The guarantor may not always find it expedient to come to the military defense of client-state allies. It is therefore in Japan's and Australia's twin interest to create a world in which the use of force by major powers is tightly fettered by the constraints of law; and to ensure that if either of them is attacked, the U.S. has the military muscle and political will to defend it.