Pope Francis is a Jesuit, and it was the Jesuits who were in Japan during WWII to promote Christianity in the country. (Look up the "Hiroshima Eight" to read about the Jesuit priests in the city who miraculously survived the blast.)
Anyway, the Jesuits were spending no small amount of time and effort to promote Christianity in the country; when they learned that a "Christian" country had dropped the bomb that caused that destruction, the entire order began a shift to the left. (They thought at the time that it had been a meteor.)
Personally, I think Pope Pius XII had a more credible approach when he decried the practice of targeting population centers in general (which was really the bigger issue at hand).
Jesuits are evil.