When he became ambassador to Russia, he was appointed chujo (vice-admiral) in the navy; this came to be because according to diplomatic customs of the time, it was judged that a military officer would have more advantage in negotiation, and Hirobumi ITO proposed it to the government.
駐露公使就任にあたって、榎本は海軍中将に任命されたが、これは当時の外交慣例で武官公使の方が交渉上有利と判断されたためで、伊藤博文らの建言で実現したものである。