Complex sentence: The majority of the navy's escorts are thirteen Type 23s, eight of the Type 23s are to be refitted and equipped with the highly capable Type 2087 towed-array sonar.
Split into simpler sentences: The majority of the navy's escorts are thirteen the Type 23s. Eight of the Type 23s are to be refitted and equipped with the highly capable Type 2087 towed-array sonar.