The following is extracted from Jim Forest's book, "The Root of War is Fear".
“Target Equals City,” an essay written [by Merton] in February 1962 and slated for publication in The Catholic Worker, was refused approval by his order’s censors, the first of Merton’s war-related writings to suffer that fate. In it he argued that a major ethical border had been crossed during the Second World War. On the Allies’ side, it was a war that that had begun with “a just cause if ever there was one.” There was no doubt that Hitler was the aggressor in Europe and that Japan was in Asia. But by the war’s end in 1945, not only Germany but the Allies had moved from bombing military targets to targeting whole cities. Those theologians who took Church teaching on war seriously were forced to consider the question “whether the old [just war] doctrine [still] had any meaning.”
"The obliteration bombing of cities on both sides, culminating in the total destruction of Hiroshima and Nagasaki by one plane with one bomb for each, had completely changed the nature of war. Traditional standards no longer applied because … there was no longer any distinction made between civilian and combatant…. [In fact] the slaughter of civilians was explicitly intended as a means of 'breaking enemy morale' and thus breaking the 'will to resist.' This was pure terrorism, and the traditional doctrine of war excluded such immoral methods…. These methods were practiced by the enemy [at the war’s start, but by the time] the war ended they were bequeathed to the western nations."
Merton recalled how, early in the war, Britain had declared that it would not imitate Germany’s savage blitz-bombing tactics but instead would limit its bombing raids to military objectives. But in 1942 Britain abandoned its early restraint and began to target whole cities. “There are no lengths in violence to which we will not go,” Churchill declared. To quiet troubled consciences, the argument was put forward that city destruction, in the long run, “will save lives and end the war sooner.” In one notorious case, a thousand British and US bombers dropped so many bombs on the German city of Dresden that a firestorm was created that gutted the heart of the city. An estimated 25,000 people were killed, including many refugees and Allied prisoners of war. Far more died or were injured in the saturation bombing of Tokyo — the Tokyo Fire Department estimated 97,000 killed and 125,000 wounded.
Merton noted that while one can understand how those who suffered the Blitz would accept similar combat strategies against their enemy, no one could any longer claim that the standards of the just war doctrine, requiring not only a just cause but just methods that shelter non-combatant lives, were being respected.
The development of nuclear weapons and rockets for their delivery to distant targets, many of which were cities, meant that city destruction had become an integral element of future war planning. While the policy is called deterrence, the effectiveness of deterrence depends on the demonstrated readiness to commit the gravest war crime ever contemplated.
Meanwhile the vast majority of Christians were offering no resistance. “The Christian moral sense is being repeatedly eroded,” Merton wrote. When occasional protests occur or questions arise, “soothing answers are provided by policy makers and religious spokesmen are ready to support them with new [moral] adjustments. A new cycle is prepared. Once again there is a ‘just cause’. Few stop to think that what is regarded complacently as ‘justice’ was clearly a crime twenty years ago. How long can Christian morality go on taking this kind of beating?”
Merton finished the essay with these three sentences:
"There is only one winner in war. The winner is not justice, not liberty, not Christian truth. The winner is war itself."