This summer will mark the seventieth anniversary of the atomic bomb’s invention and its use against two Japanese cities. The anniversary will be commemorated by rallies and speeches demanding the abolition of nuclear weapons. That has been the professed desire of most American presidents since 1945, including Harry Truman. But I’ve spoken with military officers, academics, and former Pentagon officials who think the notion of abolishing nuclear weapons is a dangerous and impossible fantasy. They would like the United States to modernize its nuclear weapons and delivery systems instead. Their arguments go something like this:

Fifty to sixty million people were killed during the Second World War. America’s nuclear weapons not only ended that war but also played a critical role in avoiding a third one. Indeed, our nuclear weapons prevented the Soviet domination of Japan and Western Europe. History has shown that traditional enemies who have nuclear weapons don’t fight wars against one another. Nuclear deterrence works. Both China and Russia are now spending heavily to modernize their nuclear forces. If the United States doesn’t modernize as well, it will appear weak. It will become an inferior nuclear power. And if the United States unilaterally reduces the number of weapons in its arsenal, allies currently shielded under its ‘nuclear umbrella’, like Japan and South Korea, will build their own nuclear weapons – greatly increasing the likelihood of a nuclear war. Tampering with a national-security strategy that has kept the peace among world powers for seventy years would be a risky and irrational move. A treaty to abolish nuclear weapons would be as effective as the Kellogg-Briand Pact, an international agreement, signed by the United States in 1928, that outlawed war.

The Catholic Church once agreed with many of those arguments. For most of the Cold War, the Vatican was staunchly anti-Communist, and nuclear deterrence was blessed as a means of containing the influence of the Soviet Union. In keeping with the Geneva Convention, the targeting of civilians and the indiscriminate destruction of cities was condemned by the Church. But at least one American bishop suggested that low-yield nuclear weapons could be used morally ‘against military objectives in a just war according to theological principles’. Dorothy Day’s pacifism was outside of the Catholic mainstream, and she was constantly at odds with Francis Cardinal Spellman, the Archbishop of New York. Spellman thought the American troops in Vietnam were ‘soldiers of Christ’ who were fighting a ‘war for civilization’. In 1982, Pope John Paul shifted the church’s position on nuclear weapons, declaring that deterrence was ‘morally acceptable’ only if it served as ‘a step on the way toward a progressive disarmament’. When the Cold War ended, the reliance on nuclear weapons to maintain world peace became harder to justify.