According to George Zabelka
The destruction of civilians in war was always forbidden by the church, and if a soldier came to me and asked if he could put a bullet through a child’s head, I would have told him, absolutely not. That would be mortally sinful. But in 1945 Tinian Island was the largest airfield in the world. Three planes a minute could take off from it around the clock. Many of these planes went to Japan with the express purpose of killing not one child or one civilian but of slaughtering hundreds and thousands and tens of thousands of children and civilians—and I said nothing.
I never preached a single sermon against killing civilians to the men who were doing it.