By the end of the 1920s, his attention turned decisively to the culture of the Nakhi people. He wrote a two volume cultural history of the Nakhi and many studies of the texts and ritual ceremonies of the Dongba, a term that refers to both the religious texts and the shaman priests who composed them. The Nakhi Dongba were prolific composers of recitation texts using a unique script typically described as pictographic, although it is better understood as a rebus-like mnemonic device that complexly combines iconic and phonetic elements. The script required intensive training to be read or interpreted, and therefore was strictly for religious purposes and largely comprehensible only by the Dongba themselves. Rock worked with a number of dongba priests to produce transcriptions and detailed readings of the most important ceremonial texts, as well as a dictionary-encyclopedia. While not the first to study the dongba script and rituals, his work is still considered the foundation of subsequent scholarship. He also collected numerous manuscripts or “books” and is responsible for the large majority (over 7,000) of the Nakhi works that exist outside of China, a third of all surviving Nakhi texts, huge numbers of which were destroyed particularly during the Cultural Revolution. With onset of World War II, Japanese aggression forced the Nationalist government of China to retreat to the far interior and Yunnan became a central supply point. During the war years, Rock was in and out of Lijiang, often undecided whether to stay and continue his Nakhi research or to leave. He spent a year in southern Vietnam, which gave him a relatively stable circumstance for writing until further Japanese advances forced him out. In 1944 the U.S. Army Map Service employed him for his geographic expertise on the Yunnan section of the exceptionally hazardous route designated “The Hump,” over which the Allies flew in supplies from India to Chiang Kai-shek’s forces in western China. Rock shipped his manuscripts prepared for publication and much of his collection to safety in Europe, but all were lost when the ship was torpedoed in the Arabian Sea. Fortunately the Harvard-Yenching Institute offered him support to return to Lijiang and reconstruct his work on the Nakhi. Working furiously despite serious medical problems, he was able to recreate and augment his lost work. However, in the aftermath of the defeat of Japan, communist forces soon took control of Lijiang (which had not