He learned Malay well enough to teach it to troops headed for the Southwest Pacific and to produce a 2-volume pedagogical text, Spoken Malay (1943). After the war, he did fieldwork on two more genetically and typologically disparate Austronesian languages, Chuukese (rendered as "Trukese" at that time) and Yapese, as a member of the Tri-Institutional Coordinated Investigation of Micronesian Anthropology sponsored by Yale University, the University of Hawaii, and the Bernice P. Bishop Museum. Out of this came his A Sketch of Trukese grammar (1965).
At the same time, he began applying his comparative method to revise and elaborate phonological reconstructions that had earlier been published by Otto Dempwolff (1934–38). A series of articles such as "The Malayo-Polynesian word for ‘two’" (1947), "The Tagalog reflexes of Malayo-Polynesian D" (1947), "Proto-Malayo-Polynesian *Z" (1951), and "Dempwolff’s *R" (1953), eventually culminated in a monograph, The Proto-Malayo-Polynesian laryngeals (1953). His application of the same methods to his own new data from Chuukese led to a monograph On the history of the Trukese vowels (1949), which brilliantly demonstrated how the nine vowels of Chuukese had derived quite regularly from the four-vowel system Dempwolff had reconstructed for Proto-Austronesian.
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