 As the NWC continued its studies , the Imperial Japanese Navy ( IJN ) annihilated the Russian Baltic Fleet at the Battle of Tsushima in 1905 . Japan had already been a concern of the U.S. Navy . Strategist and Admiral Alfred Thayer Mahan had warned then @-@ Assistant Secretary of the Navy Theodore Roosevelt in 1897 of a much greater likelihood of conflict in the Pacific than in the Atlantic . Roosevelt himself , as President of the United States , had written before Tsushima to British diplomat Cecil Spring Rice , " The Japs interest me and I like them . I am perfectly well aware that if they win out it may possibly mean a struggle between them and us in the future . " Tsushima sealed the outcome of the Russo @-@ Japanese War in Japan 's favor , signaled its emergence as a world power and began a period of rivalry with the United States over intentions in the Pacific theater , as the two now became the dominant military powers there . An immediate consequence was the four Tsukuba @-@ class armored cruisers , laid down between 1905 and 1908 . These ships were designed to carry four 12 @-@ inch ( 305 mm ) guns , a size generally allocated to capital ships and unprecedented for armored cruisers . They would be protected with 8 inches ( 203 mm ) of belt and turret armour and 3 inches ( 76 mm ) of deck armour and be capable of a speed of 20 @.@ 5 knots . The <unk> were intended to take the place of aging battleships and thus showed Japan 's intention of continuing to use armored cruisers in fleet engagements . They were also exactly the type of ships for which the college had argued unsuccessfully to add to the U.S. Navy before switching to battlecruisers . 
