Yes it was because of the war, as a matter of fact there are several apostles in the same situation. Some members think serving a mission is some sort of "rule", I am not so sure about that.
I would say that it is a general rule to which there may be exceptions. President Kimball said that every worthy young man should serve a mission, and every young man who is not worthy should get worthy. That is the rule, but there may be exceptions, as in the case of my father, who didn't have the money to serve a mission.