Nominally fought over competing interests in Korea and Manchuria, the Russo-Japanese war had a significance that far outweighed its strategic reach. Central to its legacy was its outcome - the defeat of an old European Great Power by an aspiring non-European imperial state. This outcome inspired a great deal of racial and geostrategic introspection, whilst intensifying concerns in the West about ‘Yellow Peril’ that would one day overthrow European dominance. This article argues that the impact of the Russo-Japanese War on racial thinking in Japan was as significant as it was abroad, to the extent where the conflict was understood by key intellectuals as nothing short of a race war. These figures, including political philospher Katō Hiroyuki, historians Taguchi Ukichi and Asakawa Kan'ichi, and biologist Oka Asajirō, identified the outcome of the conflict as evidence that the established Eurocentric hierarchy of races was wrong. Japan's success, they argued, showed that the Japanese race (distinct, it should be noted, from other Asians) was at least on a par with their white rivals. Furthermore, some argued that it was in fact the Russians who should be excluded from the upper echelons of the racial hierarchy. Their work reveals the profound impact of the events of 1904-1905 on Japanese self-perception and confidence - and reveals the roots of racial attitudes that continue to bedevil the nation in the 21st century.