Seventy years ago, America dropped atomic bombs on Hiroshima and Nagasaki, ending World War Two. Ever since there has been passionate debate about whether it was necessary to use nuclear weapons on Japan. Critics of the action say Japan was ready to surrender, even without the bombings, and the U.S. military’s estimate of the casualties—both American and Japanese—resulting from an invasion of Japan set for late 1945 were vastly overstated.

The critics’ case does not persuade me. Here’s why.

I’m a former naval nuclear weapons officer. I’ve stood at Ground Zero in Hiroshima and felt heartsick as I looked at the mementos of nuclear destruction housed in the museum there. My military experience showed me the horror of nuclear weapons, up close and personal. I’ve literally had my finger on the red button which could launch fiery kilotons of death to submarine crews—men whom, if I met them today at a social function, I’d probably like very much, despite differing political beliefs. I long for the day when global politics will safely allow the world to disarm and eradicate all nuclear weapons. Like Gen. Eisenhower, who said “I hate war as only a general can,” I hate nuclear weapons as only a nuclear weapons officer can. Yet as horrible as the bombing of Hiroshima and Nagasaki was, the alternative of not dropping the bombs would have been far worse for American forces—and for the Japanese as well, both military and civilian.

It is well known that Germany was rushing to develop its own atomic bomb. What isn’t widely known is that Japan was doing the same thing. In the last months of the war, two German submarines were captured en route to Japan. One had a cargo of lead, the other had a cargo of deuterium or heavy water. Both are radiation-shielding materials; both were intended to help the Japanese effort to build their own nuclear weapons.

If Germany and Japan had succeeded, history as we know it would be quite different. Most likely, you and I would be speaking German or Japanese. Just imagine a world map in which Germany ruled all of Europe and Japan ruled the Pacific. Do you think their quest for empire would have ended at our shores? I don’t.

(To be concluded)