SEOUL, May 11 -- On a mild spring evening in Seoul, Togolani Mavura stood before a hall of dignitaries, colleagues and friends to deliver what he described, with characteristic understatement, as “a long but necessary speech.”

It was, in fact, a farewell — the final public address of Tanzanias ambassador to South Korea after four and a half years that reshaped one of East Africas most quietly consequential bilateral relationships.

Diplomatic postings often pass with polite ceremony and limited imprint. Mr Mavuras tenure did not.

When he arrived in South Korea in November 2021, the world was still navigating the disruptions of the COVID-19 pandemic. By the time he departed, Tanzania had consolidated its position as one...