During his historic visit to Hiroshima and Nagasaki in 2019, Pope Francis declared that “the use of atomic energy for purposes of war is immoral, just as the possessing of nuclear weapons is immoral.”

The pontiff said the world “must never grow weary of working to support the principal international legal instruments of nuclear disarmament and non-proliferation, including the Treaty on the Prohibition of Nuclear Weapons.”

Francis’ pronouncement was clear: The very possession of nuclear weapons is immoral! Therefore, if it is wrong for followers of Jesus to possess nuclear weapons, then it is equally wrong to build and modernize them, let alone use them.
https://www.ncronline.org/news/opinion/catholics-must-act-francis-mandate-abolish-nuclear-weapons