In 1977, when I served in President Jimmy Carter's State Department, I was sent to India to dissuade that country's leaders from developing a nuclear bomb. My hosts replied that they needed to keep up with China. I said that Pakistan would inevitably follow suit and the world would become less safe.
India promised that it would not export its weapons technology. So far as we know, its leaders have kept their word. But revelations about the nuclear weapons smuggling network organized by A. Q. Khan, the father of Pakistan's bomb, confirm the danger I predicted back then. Some call Khan's network an effort to spread an "Islamic bomb," but given that North Korea was on the list of recipients along with Libya and Iran, it might better be termed a corrupt bomb.
As events in Pakistan illustrate, the spread of nuclear technology does not extend the stability that comes with mutual deterrence. Rather, it increases the prospects of corrupt leakage that may allow terrorist groups access to nuclear weapons. That makes everyone less safe. Any pathological group of extremists could destroy New Delhi, Tokyo, Paris, or any city they chose.
Now the world's attention is focussed on Iran, one recipient of Pakistani technology, as the country seemingly keenest to create its own nuclear arsenal. According to the International Atomic Energy Agency (IAEA), Iran began enriching uranium at a pilot centrifuge plant last August, and is constructing larger underground enrichment facilities.