Four years ago, I stood in a boat on the Clyde and followed the first of the new Astute nuclear submarines into Faslane.

Later the same day, I asked Sir Mark Stanhope, the First Sea Lord, why we still needed such weapons. They can be used for coastal reconnaissance, he said, and attacking land targets and for intelligence gathering. "And what does the future hold?" he said. "What is the threat to this nation in the future?"

At the time, Sir Mark's reply sounded like an attempt to justify one weapon using another: fear. But then, that's how nuclear weapons have always worked. We are supposed to need them because we are terrified someone else might have them and the terror cancels itself out. It's called Mutually Assured Destruction, or MAD for short.

The Silent War (BBC Two, Thursday, 9pm), a documentary about nuclear submarines, traced the origins of this policy: how we put all our resources into building the subs, and then so did the Soviets, and how we got to the point where we had more firepower in one submarine than all the weapons ever used in the Second World War.

Some of the submariners featured in the documentary seemed to confirm the success of this dangerous arrangement, this mutually assured destruction, when they admitted there was a real threat of them attacking the other side; others seemed to undermine it by suggesting the weapons would never have been used.

Whatever the truth, the strange pulling power of The Silent War wasn't the big terror of the submarines but the little details of the lives of the men who worked in them. The "silent" in the title referred to two things: the fact the crew had to keep noise to a minimum because sound can be picked up by enemy sonar, and the fact that the silence continued for the submariners when they got home as they were forbidden to tell their families anything about their missions.

Life was difficult too for the crew while they were on board the subs: it was cramped, hot, busy, and on top of that, there was a constant atmosphere of battle readiness. On the plus side, strong friendships were formed on board and the men felt they became part of a family, albeit a dysfunctional, violent one.

And there was something else rather curious about the men's relationship with the subs. Here was a weapon capable of destroying cities at a range of 2000 miles and yet the men saw a kind of beauty in it. Captain Anatoly Andreev, for instance, spoke movingly of what it felt like to be in a sub. "Every sea had its own colour," he said, "every time it was different."

It was only when the programme seemed to buy into this, right at the end, that the tone felt wrong. The submariners have the right to feel nostalgia for deadly weaponry, but the rest of us, including programme makers, need to be wary; we need to be careful not to feel nostalgic, we need to guard against glorifying.