Sueki Fumihiko, "Chinese Buddhism and the Anti-Japan War" in Japanese Journal of Religious Studies.
Aside from the issues related to war, I found this interesting:
At first, Leguan had a positive view of Japanese Buddhism, which was the reason he went to Japan to study when he was young. He was disappointed by the poor facilities of Kachio-dera, but he was greatly impressed by the prosperity of Buddhism when he moved around Japan. His autobiography states:
Generally speaking, when I observed Japanese Buddhism, I found that its adherents were very active in establishing various provisional methods; priests and monks have progressive ideas, are fully aware of nation and race, enter the secular world, and work for the welfare of people; therefore they are respected and widely believed by ordinary people. On the contrary, Buddhism in our country is loose and irresponsible, and is corrupt. (Leguan 1947, 103)
These are Leguan’s words, but many Chinese Buddhists who had a sense of crisis in Chinese Buddhism were astonished by the prosperity of Buddhism in Japan and thought it a model for the modernization of Chinese Buddhism. As stated above, Leguan, at that time named Yuanyin, changed his name to Beiguan because he was so pessimistic about the future of Chinese Buddhism compared with Japanese
Nowadays there is a widespread notion that Buddhism in Japan went into decline because of the married priesthood, whereas it actually was quite prosperous before WWII even with the married priesthood and even Chinese monks recognized this.
This has led me to think the decline of Buddhism in Japan had more to do with post-WWII secularization and an extremely rationalist education system.