During either peacetime or during designated periods of hostilities, service members, certain veterans, and certain military family members may be eligible to become citizens of the United States. The general requirements for naturalization to become a U.S. citizen are the same as normal naturalization process. Citizenship may even be granted posthumously.
According to the Immigration and Nationality Act Section 328, a person who has served honorably in the U.S. armed forces for at least one (1) year may be eligible to apply for naturalization, which is sometimes referred to as “peacetime naturalization.” The applicant must be 18 years of age or older, and a lawful permanent resident (LPR).
Similarly, According to Section 329, U.S. armed forces members of any age who serve honorably for any period of time during specifically designated periods of hostilities may be eligible to naturalize. Qualifying military service is honorable active or reserve service in the U.S. Army, Navy, Marine Corps, Air Force, Coast Guard, or service in a National Guard unit.
For more information: m-599