Complex sentence: Initially, there were two contacts that were picked up by her computers and were identified as warship, ranging 6 to 8 mi, but she could not stalk her targets due warships' speeds and distance between them.
Split into simpler sentences: Initially, there were two contacts that were picked up by the computers and were identified as warships, ranging 6 to 8 mi. The ship, however, could not pursue its targets due to warships' speeds and distance between them.