At least 160,000 people were killed 60 years ago last Saturday when a United States airforce plane dropped the first atomic bomb on the Japanese city of Hiroshima.
Another atomic bomb was dropped on Nagasaki four days later and by the end of that week the Japanese emperor had surrendered.
Thus began the nuclear weapons era. Its distinctive feature is that these weapons have not been used again, despite the huge accumulation of destructive power since then. The record of controlling, limiting and getting rid of these weapons still hangs in the balance between established nuclear states, aspirant ones and the mass of humanity who remain vulnerable to their destructive powers. In fact the trend is towards their greater proliferation and the development of battlefield weapons, from the use of depleted uranium in shells to research on bombs capable of breaking deeply buried bunkers.
New uncertainties in world politics have added to the dangers involved since the end of the Cold War. That had a relatively stable balance of terror to sustain it, notwithstanding how close the world came to a devastating nuclear exchange during the 1961 Cuban missile crisis. Iran announced last week that it is to proceed with a nuclear gas enrichment programme, despite the protestations of the three major European powers with which it has been negotiating. An equally fraught negotiation is being conducted by six powers with North Korea in an effort to dismantle its admitted nuclear arms programme.
Alongside these, there is a vicious power game going on to expand the number of permanent seats on the United Nations Security Council beyond the current five such members, all of which are nuclear states and determined to remain so. Germany, Brazil, Japan, India and Pakistan either have access to nuclear weapons or the industrial capacity to gain access. Only a complacent set of assumptions about the existing relatively benign balance of power between them prevents us from seeing the potential for a new nuclear competition if political talks break down. Beyond that there are the dangers that rogue states, or those which believe they are under extreme threat, will resort to nuclear blackmail. And beyond that again there looms the danger that terrorist movements would gain access to nuclear weapons.
All of this should reinforce the political determination to prevent nuclear proliferation and re-emphasise that, without nuclear disarmament, this is a formula incapable of delivering strategic stability. In recent years India and Pakistan have crossed the nuclear threshold, while Libya is the only state to have gone the other way. The objective should be to get rid of nuclear weapons, however utopian this may seem. That means holding existing nuclear states to such a commitment and maintaining international pressure for linking non-proliferation to nuclear disarmament - despite last May's setback on the Non-Proliferation Treaty. Ireland has a role to play in this endeavour, given our record on initiating and sustaining the treaty.