I knew someone whose hevruta ran back to America when the first Gulf war broke out. He was immediately called up by his reserve unit and sent to Saudi Arabia. I also heard of an Israeli who ran to America and was killed in an auto accident.
The fact of the matter is everything is dangerous. Crossing the street is dangerous. The question is how dangerous and why someone is accepting the danger. For example, it is permitted for parnassa if it is something that people normally do (e.g. construction work). Moreover, conquering EY is a milchemet mitzva and that obviously pushes off. Where in EY one lives is not particularly important except perhaps for the areas that were part of Jerusalem during the time of the Bayit Sheni.