I'm reading Churchill's biography of WWII, and during his discussion of one of the early naval battles after Pearl Harbor (I can't remember which one, but I think the observation comes from "The Grand Alliance"), he comments that the Japanese language was ill-suited for naval command -- in other words, that it was somehow more difficult to communicate because of the language. Was Churchill just stereotyping, or is there any other evidence of this?
Churchill is absolutely stereotyping, and is making a causal, unsourced (I pulled my copy down and checked) and unsupported comment.
Churchill wrote in 1950, over 60 years ago, and within a decade of most of the events discussed. Since then, there has been several generations of scholarship and our ideas of what the Japanese Navy was trying to do and why have become much more sophisticated. In 1950, there really wasn't much available in either English or Japanese language about how the Imperial Navy actually planned, trained, worked and fought. He's just filling the gap in understanding with whatever seemed logical to him, and cultural stereotypes, even racism, seemed logical to a lot of British and Americans in 1950.
The current generation of English language scholarship about the Pacific War Japanese military and society doesn't really feel the need to address any peculiarities of the Japanese language as a cause of the results. There are so many other, more likely factors (i.e. the basic doctrine of the Navy, technological factors, etc.) that it really doesn't even seem worth debunking. Frankly, it just seems obviously wrong to modern readers based on how much more interaction western culture has had with Japan in the last half century and more.