Complex sentence: It was difficult and demoralizing for the US Navy personnel to mothball or scrap their newly built ships-ships that took a year or more to build and could still perform their intended function if a new war broke out.
Split into simpler sentences: It was difficult and demoralizing for the US Navy personnel to mothball or scrap their newly built ships. Ships that took a year or more to build and could still perform their intended function if a new war broke out.