How many nuclear weapons and delivery systems does a country need as an effective deterrent against the threats of attack? Finding an acceptable balance is critically important in Asia, where four of the world's nine nuclear-armed states are located.

The Stockholm International Peace Research Institute (SIPRI) reported in June that all four Asian nations with nuclear weapons — China, India, Pakistan and North Korea — appeared to be expanding their arsenals while the United States, Russia, France, Britain and Israel were either reducing them or holding the number static.

Asia may be sliding into a nuclear arms race, aggravated by underlying tensions and mistrust. As one nuclear weapons state enlarges its arsenal, other regional atomic powers do the same. SIPRI estimated that China, India and Pakistan had each added about 10 warheads to their operational stockpiles in 2012.