eight o'clock in the morning
The Japanese cruiser _ Yakumo _ , approaching from the North , had been painted white like the American cruisers , and this is why she had been taken , as the reader will remember , for the armored cruiser _ New York _ , which was actually lying off San Francisco assigned to Admiral Crane 's yellow fleet . The _ Yakumo _ was to prevent the two destroyers _ Hull _ and _ Hopkins _ from escaping from the Bay , and both boats were literally shot to pieces when they made the attempt . This action hopelessly isolated the maneuvering fleets . By eight o'clock in the morning Togo 's squadron , consisting of the flag-ships _ Satsuma _ , the _ Aki _ , _ Katou _ , _ Kashimi _ , _ Mikasa _ and _ Akahi _ , and forming the backbone of the Japanese battle-fleet , had succeeded in locating Admiral Perry 's squadron , thanks to intercepted wireless dispatches . The Japanese refrained from using their wireless apparatus , so as to avoid attracting the attention of the American squadron . The unfinished message sent at nine o'clock from Magdalen Bay told Togo that the surprise there had been successful , and a little later the order to strengthen the American advance , sent in the same way , enabled him to ascertain the exact position of both the main group of cruisers and the scouts and lookout ships . Similarly it was learned that the latter were extremely weak , and accordingly Togo detached four armored cruisers , the huge new 25-knot _ Tokio _ and _ Osaka _ , and the _ Ibuki _ and _ Kurama _ , to destroy the American van , and this he succeeded in accomplishing after a short engagement which took place at the same time as the attack on Perry 's armored ships .