On January 31, 1942, a combined Japanese force launched a two-pronged attack on the island of Ambon. Within four days, the Japanese controlled the island, city and airfield. Nellie Jansen, the Dutch resident’s daughter, provided us an eye-witness account of the early days of the occupation. As a volunteer and trained nurse’s assistant, her observations center on medical resources and organization, including the presence of Japanese doctors and pharmacists from the first week of the occupation. She also observed the use of Malay dictionaries by Japanese authorities; for example, she wrote of her chat with a wounded officer: “Dat feit scheen hem erg te vermaken, want hij greep schuddend van het lachen zijn maleise woordenboekje en zei, na er in te hebben gebladerd: “Doeloe besar, sekarang ketjil....”. This article explored what bilingual Malay-Japanese dictionaries were available to Japanese military and civilians who occupied Indonesia. The focus was on the 1942 edition of Masamichi Miyatake’s Kamoes Baroe Bahasa Indonesia-Nippon, first published in 1938. The semantic field studied in this article was medical terminology. Some of these medical terms were selected for comparison with Malay-English dictionaries available at the time, in particular Wilkinson, Winstedt and Wilkinson. This paper is part of a project to examine and evaluate lexicographic resources developed by early twentieth century Japanese scholars and to situate that seldom-studied Japanese scholarship in the global tradition of Malay lexicography.