Chinese and Korean protests over "revisionist" Japanese histories of World War II are well known. The impact of contested Chinese and US histories of the Korean War on US-China relations today has received less attention. More broadly, there has been little research seeking to systematically explore just how history textbook controversies matter for international relations. This article experimentally manipulates the impact of nation (US/China), of source (in-group/out-group textbooks), and of valence (positive/negative historical narratives) on measures of beliefs about the past, emotions, collective selfesteem, and threat perception in present-day US-China relations. A 2 x 2 x 2 design exposed randomized groups of Chinese and US university students to fictional high school history textbook accounts of the Korean War. Findings reveal significant effects of nation, source, and valence and suggest that the "historical relevance" of a shared past to national identities in the present has a dramatic impact on how historical controversies affect threat perception.KEYWORDS: Korean War, US-China relations, historical relevance, history textbooks, threat perception, anxiety, anger, pride t is well known that historical disputes underlie much of the mutual suspicion and hostility that plagues northeast Asian international relations today. Whether it is Chinese and Koreans protesting "revisionist" Japanese histories of World War II (e.g., Rose 1998), or Koreans protesting Chinese claims that the Goguryo Kingdom was Chinese (e.g., Gries 2005), history appears to be an endless source of friction in the region. As Gerrit W. Gong (2001, 26) '" Indeed, Gong (2001, 32) goes so far as to argue that "strategic alignments" in East Asia "will increasingly turn on history." Less attention, however, has been given to the role that historical conflicts play in US-China relations, arguably the most important bilateral relationship of the twenty-first century. A number of scholars have argued that Chinese nationalism today is closely tied up with narratives of China's past victimization at the hands of Western and Japanese imperialism, and that nationalism has an impact on China's foreign policies in general and US policy in particular (e.g., Fitzgerald 1999;Gries 2004;Callahan 2004). The circumstantial evidence is compelling. For instance, following the NATO bombing of the Chinese Embassy in Belgrade in 1999, the People's Daily, the official mouthpiece of the Chinese Communist Party (CCP), published an editorial titled, "This is not 1899 China." It passionately declared, This is 1999, not 1899. This is not ... the age when the Western powers plundered the Imperial Palace at will, destroyed the Old Summer Palace, and seized Hong Kong and Macao .... China is a China that has stood up; it is a China that defeated the Japanese fascists; it is a China that had a trial of strength and won victory over the United States on the Korean battleground.... U.S.-led NATO had better remember this.The Belgrade bombing, in this Chinese view, was ...