The goals and themes of this work have undergone substantial change in the course of the basic research. As originally conceived, this monograph was to explore the political and diplomatic relationship between the Mongolian courts of China, the Yuan, and Iran, the Il-qans/Il-khāns. I was particularly interested in their joint efforts to stave off the military challenge of their rivals and cousins in central Asia, the lines of Chaghadai and Ögödei, and the western steppe, the line of Jochi, in the last half of the thirteenth century and the early decades of the fourteenth century. To sustain one another against their mutual enemies, the regimes in China and Iran shared economic resources, troops, and war matériel. As time passed, I became increasingly aware that this exchange was far more wide-ranging and diverse, embracing as it did an extensive traffic in specialist personnel, scholarly works, material culture, and technology. My interest in these issues grew and I soon came to the conclusion that these cultural exchanges were perhaps the most consequential facet of their relationship.

This, however, was only the first phase of the work's transformation. Having settled on the issue of cultural exchange as the central theme, I naively assumed that I would proceed by identifying specific exchanges and then assess their “influence”: for example, the impact of Chinese physicians in Iran on Islamic medicine. This, I quickly discovered, posed formidable problems of method, interpretation, and evidence.