General David Richards is one of Britain’s most influential soldiers: he served as head of the British Armed Forces and NATO commander in Afghanistan. But he is perhaps most renowned for his humanitarian intervention in Sierra Leone in May 2000, when he unilaterally took decisions on the ground to protect the capital, Freetown, saving the country from sliding into genocide.

He spoke with war reporter Janine di Giovanni, who has covered conflicts including those in Bosnia, Iraq, Afghanistan, and Syria.

A: I knew that it was possible to fail because of the number of tactical challenges. And of course I had to persuade London to back me. But I had been to Sierra Leone three times before, and I had a good grasp of the issues and the nature of the enemy, the Revolutionary United Front (RUF). With a bit of luck, I would pull it off. Napoleon said “Give me lucky generals.” That said, without good people in key positions, I never could have managed. If I really thought I was going to fail, I wouldn’t have tried it. It was a risk, but not a gamble.

A: I was conscious that the genocide in Rwanda had happened not long before—military commanders had been too cautious and followed bad orders. In Sierra Leone, I was determined that I would avoid such an outcome. If I played my cards right, at a minimum I could prevent the RUF from getting into the city. But yes, you’re right, I had no orders to do this.

A: The primary difference was that Sierra Leone involved the British collaborating with others but calling all the shots. In Afghanistan, everyone took orders primarily from their own capital. If they felt like it and it suited their national priorities, they would also take orders from me. People did their best, but one or two nations were very difficult. Subordinate commanders, usually put up to it for political reasons by their national bosses, would second-guess me. They could undermine perfectly sound military logic. In Sierra Leone, everyone was indisputably on the same side and wanted the same outcome.

A: At a conference a few years ago, I heard a serving US officer discuss nuclear weapons as if they might be used as an integral part of modern war. I and a few other Cold War diplomats and politicians were horrified. They are the most dreadful weapon: if we use them, we have failed. They must be seen as a deterrent—something whose possession makes war less likely, not more.

For that reason, we need to persuade Iran not to develop nuclear weapons. President Trump is now using a very harsh sanctions regime to achieve this, but I worry that he is underestimating and misreading the Iranians. Like the Russians, they will sustain a great deal of pain to achieve their goals. It would have been better to stick to the nuclear deal and play the long game. The trouble is the West is divided. This is the worst of all worlds. We need to be united around the nuclear deal or the president’s alternative. The Iranians are sophisticated, and they will exploit that wedge.

A: It’s inevitable. These things will change the character of war, but not the nature. After the tank was invented, for many years it was very successful and dominated warfare; today its utility is more limited. And as we go through this tech revolution, this doesn’t necessarily mean that conventional armed forces and weapon systems will become redundant. You can probably never have enough technology to deal with a million people and 50,000 tanks. The new systems have to be capable of defeating old forms of industrial warfare.

A: My instinct is that war is sadly inevitable. We should always assume that there are people out there who are prepared to achieve their goals through war. Even if we don’t want to go to war, others may in order to achieve their aims. The best defense against this is to be strong enough to deter it. But when no alternative exists, we must be prepared to root out evil in its infancy and before it becomes endemic.