Alison Utley flies in the plane that carried the A-bomb and, together with a peace studies lecturer and his MA students at Bradford University, decides whether to bomb Nagasaki.
If this was physics, we could replay it and take out the atomic bomb. But social scientists can't do that." Instead, Oliver Ramsbotham asks his postgraduate audience to replay in their minds the events of August 9, 1945 on the Japanese island of Tinian.
"We are with the US 509th composite force whose mission is to drop the second atomic bomb. We will be travelling in the plane carrying the bomb," he tells them. The fiction in the simulation is that we will decide whether or not to drop the bomb.
As an exercise in applied ethics, case studies do not get much more controversial. The aim is to uncover some of the depths of sincere disagreement that arise in conflict. It is too easy, Dr Ramsbotham tells us, to sit in our armchairs and play with ideas. The choice is simple: we drop the bomb or we do not. "Remember, we are the policy-makers who bear responsibility for the eventual outcome," he says.
A show of hands at the start gives a rough 50/50 split between supporters of dropping the bomb and opponents and a few are undecided.
Arguments for and against are passionately contested. The strongest argument in favour of the bomb is, oddly, that it will save lives - in the long run. After all, in one night of conventional bombing in Tokyo, 83,000 lives were lost.
One student throws up his hands: "In my city, in Lebanon, we were bombed continually. They don't care about saving lives, they want to win the war."
Now we are en route to our target complete with plutonium bomb.
Where is our target, Dr Ramsbotham asks? Trick question. It is not Nagasaki but Kokura. Due to heavy cloud cover, the plane flies on to Nagasaki. "A chilling thought," he says. "If it had been a sunny day there ..."
We arrive. There is only enough fuel for one run. Then the crunch: "Those who abstained got away pretty lightly," Dr Ramsbotham says ominously. "You are going to decide. Do we or don't we?"
He starts counting backwards from ten. The decision is quick. The bomb will not be dropped. "You see, when it really comes to it, all the time you were on one side or the other. You have to be or history will just roll over you."
An uncomfortable silence fills the room and we file out slowly. One student tells his neighbour never to miss this class. "Some others are so boring," he says. "But after this class, I always come out thinking hard."
Bradford's MA in peace studies explores some of the most difficult questions facing the human race. Analysing the relationship of peace and violence, peace and conflict, and peace and war, students look at the circumstances, if any, in which the use of military force can be justified.
Dr Ramsbotham is a former school teacher and he finds lecturing to such an international audience with such varied experience a challenge.
"If you assume no knowledge you risk losing the most sophisticated students," he says. "The trick is to include some deeper concepts to be taken up by the more advanced members of the group. The use of live controversies helps."