The factor that made Japanese military forces especially deadly was:
C) Japan's soldiers were taught to fight to the death rather than surrender.
This mentality was deeply ingrained in Japanese military culture during World War II. Japanese soldiers believed that surrender was dishonorable, and they were often instructed to fight fiercely and not give up even in the face of overwhelming odds. This led to intense battles where Japanese forces fought tenaciously, causing high casualties among both the Japanese troops and their enemies. This commitment to fighting to the death made Japanese military forces formidable opponents during the war.