What is the theme in War and Remembrance by Herman Wouk?

Duty is one of the overriding themes of the book, especially as seen in the lives of the various officers. Pug sacrifices time with his family in order to do his duty. He admits he has often left Rhoda alone while he was on some trip associated with his military career. While his career is important and he believes he is in line for another sea mission, Pug is called on by President Roosevelt to take on other duties that will certainly not give him the career boost he is hoping for.