 The Nagato @-@ class battleships ( 長門型戦艦 , Nagato @-@ gata senkan ) were a pair of dreadnought battleships built for the Imperial Japanese Navy ( IJN ) during World War I , although they were not completed until after the end of the war . Nagato , the lead ship of the class , frequently served as a flagship . Both ships carried supplies for the survivors of the Great Kantō earthquake in 1923 . They were modernized in 1933 – 36 with improvements to their armor and machinery and a rebuilt superstructure in the pagoda mast style . Nagato and her sister ship Mutsu briefly participated in the Second Sino @-@ Japanese War in 1937 and Nagato was the flagship of Admiral Isoroku Yamamoto during the attack on Pearl Harbor on 7 December 1941 that began the Pacific War . 
