 "Aoba" and "Kinugasa" were otherwise built on the same hull as "Furutaka" and "Kako", with identical machinery and armor.As built the "Aoba" was more than 900 tons heavier than its design weight, with negative effects on the performance of the ships similar to that of the "Furutaka" class overweight condition.In 1930, the Naval General Staff, concerned by the limitations on the size of their navy by the London Naval Treaty won approval for an extensive modernization program of the "A class" cruisers.