Oddly enough, there are no Operas set during the Korean War. To make up for this, here are some suggestions (feel free to add your own):
Collina Cotoletta Porco,
Il Perimetero Pusano (featured aria, "MacArturo, non piscio in Yalu"), and, finally,
Un Ballo in MASH (with climatic duet, "O Franco! O Margaretta!).