Complex sentence: Although currently South Korea is under the U.S's nuclear umbrella of protection, it could very well break away and try to develop its own nuclear weapons if neccesary as like Japan, South Korea has the raw materials and resources to create nuclear weapons.
Split into simpler sentences: Although currently South Korea is under the U.S's nuclear umbrella of protection, it could very well break away and try to develop its own nuclear weapons if neccesary. Like Japan, South Korea has the raw materials and resources to create nuclear weapons.