Complex sentence: Superior underwater combat training would likely decide which two groups of frogmen would win; generally, criminal or terrorist frogmen only have access to types of training which are available to civilians, or at least inadequate facilities.
Split into simpler sentences: Superior underwater combat training would likely decide which two groups of frogmen would win. Generally, criminal or terrorist frogmen only have access to types of training which are available to civilians, or at least inadequate facilities.