About 20-25 years ago I was active in CND at Sussex University and I was as ready as anyone to condemn the USA, especially during the Reagan years. And I don't think anyone with any sense can regard the attacks on Hiroshima and Nagasaki as anything other than horrific. But...

There's a lot of 20-20 hindsight being expressed here. I don't think I would have acted differently if I had been Truman. Yes, the attacks cost hundreds of thousands of innocent lives but by the end of the war millions of innocent lives had already been lost (including some 15 million in China under Japanese occupation).

I don't doubt that Truman would have been aware of the implications of his decision. How much he cared I can't say.

However, I do feel that by the time of the attacks Truman's chief responsibility was to end the war with as little loss of American and allied lives as possible. The Japanese government had chosen to take their country to war (initially against China, which is when World War 2 really began)and it is they, in my view, who bear the brunt of responsibility for the consequences for the Japanese people - not the Americans.

And while it's an awful thing to say, perhaps the attacks were a necessary lesson for the rest of the world in how destructive another world war would be. If the attacks hadn't taken place and at least been perceived to have been the blow that finally ended the war, it's quite likely in my view that either the US or the Soviet Union would have been tempted to use the bomb in a subsequent war, such as Korea- perhaps in the mistaken view that the bomb could have been used like any other weapon. The perception of the bomb as an ultimate weapon, whose use was to be avoided at all costs, stemmed from the evidence of Hiroshima and Nagasaki - in other words, what the bomb could really do to real people.

Much of the subsequent criticism of Truman's decision stems from the view that the attacks were intended as a lesson to Stalin and, as a result, they led to the Cold War. There may be an element of truth in that but I don't believe that Stalin's attitude to Poland and Eastern Europe (for instance) would have been significantly different if the bomb had not been used on Japan. The Cold War had much deeper roots than that.

There are, of course, lots of 'what if's. What if the bomb had not been used? Would Japan have surrendered or would elements in its armed forces have forced the country to fight to the death? This would have seemed an unacceptably high probability to the Americans at the time, especially after the experience of Okinawa, where civilians committed suicide in huge numbers because they had been indoctrinated to believe an American occupation would be worse.

If Japan had surrendered first, would the bomb have been used to end the war against Germany? Or would it have been considered less acceptable to use it against europeans (I personally think that is quite likely)?

If Truman had waited, or offered Japan terms sooner, would the war have ended without an invasion or the use of the bomb? Maybe, but by 1945 the one thing the allies were all united on was the demand for unconditional surrender. A negotiated peace on any other terms was never likely to be an option in the context of the time.

It should also not be forgotten that the use of the bomb was a huge gamble. It was by no means certain that the devices would both work (especially as they were both of different designs) and there had only been one solitary test of a live bomb before the attack on Hiroshima. These days it would be unthinkable for a revolutionary new weapon to be deployed strategically with so little testing. The fact is, no-one really would have known what was going to happen at the time. Apparently the US only had three bombs ready for use. If Japan had decided to fight on it would have been back to square one with the invasion.

Yes, the US has done plenty of things both before and since World War 2 that can and should be condemned and as I said at the beginning, no reasonable person can regard Hiroshima and Nagasaki with anything other that the most profound horror and sorrow. It was a cataclysmic end to a cataclysmic war, and one in which in a few short years saw mankinds ability to inflict suffering upon itself progress (if that's the right word) in ways that could not have been imagined before. But in the end, I doubt that I would have made a different decision: to launch a huge and costly invasion or to pin one's hopes on two more air raids at the end of a war that had already seen millions of people die as a result of aerial bombardment?

Hiroshima and Nagasaki must be remembered and never repeated and in my view, the case for nuclear disarmament is as strong now as it was 25 years ago. If we want to honour the memory of all the innocent people who died in World War 2, whether from Nazi atrocities, starvation and forced labour in Japanese prison camps, allied incendiary attacks or the atomic bomb, we need to remember the attacks as a lesson for all of us. To do anything less would be an atrocity.