[Nathan Zachary]

"Of all the secondary targets to pick, Nagasaki was the center of Japan's largest Christian community."

Where did you hear that? It was an industrial area

[usmcobra]

That is a historical fact.

It was the site of Urakami Cathedral or St. Mary's Cathedral built by the Kakure Kirishitan or "Hidden Christians".

[Does so]

"Of all the secondary targets to pick, Nagasaki was the center of Japan's largest Christian community."

Where did you hear that? It was an industrial area

Probably here at FR; however, Amazon books gets a great many references from Google, and here are two others:

http://www.americancatholic.org/Features/WWII/feature0283.asp

http://findarticles.com/p/articles/mi_m1141/is_35_41/ai_n15341010

Another footnote:

"...Survivors from the Catholic community--the bomb had fallen on Nagasaki's Catholic district and cathedral--..."