Chosin is netiher a Japanese nor Korean pronounciation of Morning Calm.<<
An explanation: In 1950 American military maps of Korea were copies of the
Japanese Military Survey, 1928 (with a few updates and corrections.) The
Japanese military maps used "Kanji" for all place/terrain names. Given the
rush for maps, the American military map service in Tokyo had translators
"Romanize" the Kanji and the Romanization was printed on the maps along
with the original "Kanji." It was a hurried job and there were a lot of
errors. (As a matter of information, the maps were not all that accurate to
begin with.) Thus the Changjin Reservoir appeared on these maps as the
"Chosin Reservoir." The two Kanji for "Chosin" are entirely different than
those for Japanese Kanji for Korea.