Mogami had two identities: a nominal light cruiser armed with five triple 155 mm turrets and a later heavy cruiser with five twin 8-inch turrets. Its official 8,500-ton figure bore little relation to a final standard displacement above 13,000 tons and a full-load figure that estimates place still higher. Replacing the 155 mm battery with heavier guns and their supporting structures contributed substantially to the growth. The original fifteen-gun light-cruiser form offered overwhelming forward fire and may have fitted Japanese needs better. The conversion produced a powerful heavy cruiser, while reinforcing the five-turret compromise criticised throughout the lecture.
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Mogami's change from light cruiser to heavy cruiser
Mogami began with fifteen 6-inch guns, then became a ten-gun 8-inch cruiser as its displacement rose dramatically.