Over 100,000 Americans died in vanquishing the Japanese Empire from the South Pacific and the face of the earth. An estimated 50-60 thousand are still listed as missing in action there. This month, the the remains of 8 of a 10 man B24 bomber missing 70 years were brought home from the jungle of a South Pacific Island and interred at Arlington National Cemetery.
Secondly, advances in military technology have changed the face of military campaigns completely. During World War II the U.S. had 12 million people serving in the military. That was about 10% of the U.S. population. That would be the equivalent of having about 31 million military personnel today -- at a time when having even 5 million would bankrupt this country.