Military service in a foreign country is not an expatriating act if service is as a soldier who is not an officer, unless the foreign military is engaged in hostilities with the United States. Further, foreign military service usually does not cause loss of nationality since an intention to relinquish nationality normally is lacking. In adjudicating loss of nationality cases, the Department has established an administrative presumption that a person serving in the armed forces of a foreign state not engaged in hostilities against the United States does not have the intention to relinquish nationality. One who voluntarily serves as a commissioned or non-commissioned officer in the military of a country not engaged in hostilities with the United States will lose one’s U.S. citizenship only if one intended to relinquish U.S. citizenship when he/she served in the armed forces of a foreign state.
Mast wasn't even serving as a soldier at the time - he was a double amputee volunteering to pack medical kits and move supplies.
Subsec. (a)(3). Pub. L. 99–653, § 18(d), as amended by Pub. L. 100–525, § 8(m)(2), [ changed from ] for “unless, prior to such entry or service, such entry or service is specifically authorized in writing by the Secretary of State and the Secretary of Defense
That's what I was remembering. It used to require a bunch of permission letters to do this, and now it's just "oh, hey, you still want to be an American? Coo'."
That is explicitly false:
Mast wasn't even serving as a soldier at the time - he was a double amputee volunteering to pack medical kits and move supplies.
From the Cornell link in that page:
That's what I was remembering. It used to require a bunch of permission letters to do this, and now it's just "oh, hey, you still want to be an American? Coo'."