This paper attempts to shed light on issues of trust, control, ethics and identity concerning military interpreters who use their language skills against the country or people of their own cultural heritage. It examines linguists (translators and interpreters) who worked in military intelligence and operations during the Pacific War and the occupation of Japan, and military linguists involved in the current context of the “global war on terror”. Drawing on Cronin’s notion (2002, 2006) of heteronomous and autonomous interpreting systems, this paper discusses different sourcing avenues of military linguists during and after the Pacific War: Caucasian linguists trained at US military Japanese schools as autonomous, Japanese nationals locally hired for the occupation as heteronomous, and Nisei (second-generation Japanese American) linguists as in-between. Parallels and comparisons are drawn between the ambiguous standing of those Nisei linguists and the situations of foreign-born US military interpreters and locally hired civilian interpreters in Iraq and Afghanistan. The complex and difficult challenges faced by military interpreters who utilize skills deeply rooted in their heritage against their own people or people of their cultural heritage should be visited in future discussion of government policies for recruiting, training and utilizing heritage language linguists in military settings.