Re Ishiwara: Mark Peattie's book remains unsurpassed for English-language works. I've published a short commentary on his Pan-Asianism and translation (excerpt) from a pamphlet by his Far Eastern League in the Routledge Handbook of Modern Japanese History.

The edited (Peattie, Drea, et al) volume The Battle for China has some good chapters on the army (and navy, e.g., their role in bombing Chinese cities). Forgot to include the title for Peattie's monograph: Ishiwara Kanji and Japan's Confrontation with the West (if memory serves).