During the postwar and Cold War period, the status and image of Japan in the United States took on a rapid transformation?from America’s enemy to an indispensable ally. As the US needed Japan as a valuable partner in the Cold War, American efforts to recreate and circulate a new and agreeable image of Japan appeared in various areas, ranging from political arenas to Hollywood films and art museums. In tandem with American endeavors and in an effort to promote its national image as a new cultural power, Japan attempted to replace its jingoistic image with an aesthetic one and circulated its art and ideas throughout the US. Demonstrations of Japanese art and culture, including Zen aesthetics, were positively and often enthusiastically received among Americans in general despite the strong nationalistic stance of prominent New York critics who championed Abstract Expressionism as “the American-type painting” and denied/ignored any kind of “oriental” influence on mainstream New York artists. The study and utilization of Zen became a widely spread phenomenon among postwar American artists and intellectuals. Many American artists, including Mark Tobey, Morris Graves, Ad Reinhardt, Isamu Noguchi, Ibram Lassaw, John Cage, and the Beats, took part in the “Japan boom” and “Zen boom.” The appropriation of Zen and Asian aesthetics by American artists during the postwar and Cold War era is now viewed as a summit of cultural/artistic interchanges between the US and East Asia, an aesthetic fusion of the West and East in the history of American art. However, in a discussion about Zen in the field of American art, we are bound to ask: whose Zen and which Japanese aesthetics did American artists encounter? Zen in American art has kept much stronger ties with Japanese Zen rather than with either Chinese Chan or Korean Sun. In disseminating Japanese aesthetics, Japanese art and Zen experts played the role of cultural diplomats by fostering specific aspects of Japan’s cultural heritage and advocating their ideal of Japanese Zen and art among American artists and the public. The popularity of Zen Buddhism was generated by the teaching and proselytizing activities of Japanese Zen proponents and popularizers such as Shaku Soen, head abbot of the Engakuji branch of the Rinzai Zen sect, and his protege, D.T. Suzuki, as well as Okakura Kakuzo, Alan Watts, and Sabro Hasegawa, who visited or lived in the US from 1893 onward to cultivate Japanese Zen Buddhism and aesthetics in the US. In postwar America, Sabro Hasegawa, while formulating Japan’s modern art of national identity, took an important part in boosting the Zen boom and love for Japanese aesthetics in the US, to the extent that people joked the Japanese government should appoint him as an “art ambassador” for his role. Also, D.T. Suzuki, known as the most influential figure on Zen Buddhism in the West and whose teachings were employed by American artists, aggressively promulgated Zen. He contributed to making Japanese Zen more appealing and less threatening to Western audiences through his universalization of Zen by underlining its applicability to all cultures and areas as well as its aesthetic aspect. This examination of the presence of Japanese nationalism in postwar American art suggests that a particular sect of Japanese Zen worked as a means of cultural diplomacy to build, recreate, and restore the ideal and supreme image of Japan in the West from the last decade of the 19th century onward. A sect of Japanese Zen, introduced and popularized in America, was rooted in “New Buddhism (shinbukkyo),” which was originally produced in order to be in line with the Japanese government’s nationalist and imperialist policy, as expounded in recent studies by Robert Sharp and Brian Victoria. Accordingly, Zen of “New Buddhism” was presented to American and European audiences as the heart of Japanese culture as well as the spiritual and aesthetic quintessence of the Japanese people. Furthermore, contending against the Western Orientalist attitudes, Japanese Zen adherents fostered and propagated the “Reverse Orientalism” theory, Toyoshugi , which constructed the intellectual and cultural supremacy of the East (Japan) over the West. This theory corresponded to the ideas of Shaku Soen, D.T. Suzuki, and Nishida Kitaro of the Kyoto School and was absorbed in the teachings and writings on Zen by experts such as Okakura Kakuzo, Alan Watts, and Eugen Herrigel, thus all the more affecting American artists’ understanding and utilization of Zen aesthetics. American response to Japanese Zen and aesthetics differed to a varying degree among artists, writers, and media?shaped by individual needs and sensibilities?but they often seem to have subscribed unwittingly to Japan’s nationalist ideas in their art.