that as it may, please consult and report to the Korean embassy/consulate
about your acquisition of the U.S. citizenship and follow their instruction.
Below please find an official reply posted on the MMA website, which
corresponds to your inquiry. Mr. YH Joh in Korea appears to be able to
explain in English for your better understanding. If you need any assistance in filing Korean documents, just let our offices know. Hope it helps!
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"According to Nationality Law, a national of the Republic of Korea
who voluntarily acquires foreign nationality forfeits his/her
nationality of the Republic of Korea upon acquisition of the foreign nationality.
Furthermore, according to Military Service Law, military duties to the Republic of Korea are only imposed on the nationals of
the Republic of Korea. If you acquire foreign nationality (citizenship) after birth and thereby forfeit the nationality of the Republic of
Korea, your military duties are forfeited accordingly (re-imposed
upon reacquisition of Korean nationality), and in this case, your departure or entry will not be restricted for reasons regarding
military service. If you have any further questions, please contact
the Military Resources Service Division of MMA (+82-42-481-2757,
person in charge: Joh Yong-hoon).
국적법 따라 대한민국의 국민으로서 자진하여 외국 국적을 취득한 자는 그 외국국적을 취득한 때에 대한민국의 국적을 상실하게 됩니다. 또한, 병역법에 따라 대한민국의 병역의무는 대한민국 국민에 한하여 인정되며, 외국국적(시민권)을 후천적으로 취득하여 대한민국의 국적을 상실한 경우 병역의무가 없게 되며(국적 재취득시 병역의무 부과), 이 경우 병역과 관련하여 출입국에 제한을 받지 않습니다. 그러므로 거주지 재외공관이나 법무부에 외국 시민권 취득을 신고하시기 바랍니다."