Talk:Norden Incident/@comment-191.54.160.77-20180802221234/@comment-33588379-20180803115250

Based on the term the original novel used, it refers to ノルデン戦区. Theater is a military term refers to an area or place in which important military events occur or are progressing. You may get more information from wikipedia.

https://en.wikipedia.org/wiki/Theater_(warfare)