Simple question that has bothered me for a while, but I never through to ask. Why is the word "Tokyo" constantly translated and spelled as Tokio in American propaganda during the war? Is this similar to why we have Beijing and Peking for the same city, and just transliteration?
Google Ngram Viewer shows Tokyo pulling ahead of Tokio in English around 1900 and dominant ever since. Tokyo instances increased more rapidly around the 1920's while Tokio showed a gradual decline, already down more than 10-1 by 1940, and declined faster from about 1945.
The only newspaper database I can easily search is the Chicago Tribune, and I notice several decades of overlap: stories in which both spellings appear at least once.