I just found out that Jiryu Mark Rutschman-Byler has made his MA thesis, Sōtō Zen in Meiji Japan: The Life and Times of Nishiari Bokusan, free for all to read.

[... W]hat I discovered in my study is obvious but important: the world of [Shunryū "Zen Mind, Beginner's Mind"] Suzuki Roshi's Zen training had very little to do with the world of Dōgen Zenji's Zen and Chan training. The Zen world that Suzuki Roshi trained in — a world he shared generally with people like Kishizawa Ian and Kōdō Sawaki and Hakuun Yasutani and Taizan Maezuki and Jōshū Sasaki — was not only centuries removed from Dōgen's monasticism but was in fact a world that had already been influenced by the West, had already been modernized and to some agree adapted to Western sensibilities and epistemologies.

In other words, much of the transformation of Zen that I have assumed took place in the West in the mid to late twentieth century in fact took place in Japan somewhat earlier. Specifically, it took place over the course of the Meiji Period (1868-1912) [...]

One undeniable proof of Zen's adaptation to the US: roshi, though loaned directly from Japanese rōshi, doesn't get any diacritic on its long "o". (Its usage is also subtly different in the English-speaking world — Stuart Lachs, for example, has argued that to English speakers "roshi" is used like "master" with the implication of some kind of spiritual or other attainment, while in Japan it often simply indicates seniority. The etymology of the word, after all, is just "venerable teacher" 老師.)

Jiryu (another macronless loan!) has also been writing a series of posts at his blog summarizing and ruminating on his findings, starting with Sex, War, and the Problem of Zen Precepts and Who Westernized Zen?

The precepts are a kind of empty space, and while the rhetoric of Zen precepts is that that space stays empty until filled by the needs of the situation, more often, I'm afraid, they just allow any preexisting views to come forth as the "flexible" or "appropriate" expression of precepts.

How else to explain Nishiari's support of the imperialist wars as in line with precepts and modern American Buddhist tolerance for sex out of wedlock as in alignment with the precept against fornication? These positions are more about the values of the social context than they are positions somehow dictated or even informed by Buddhist precepts.