USCIS officials said the drop in applications is not due to any action by their agency, which processes the applications as it receives them.
"The fall in military naturalization applications is likely attributable in significant part to the Department of Defense's decision not to renew the Military Accessions Vital to the National Interest (MAVNI) program after its expiration at the end of FY17," USCIS said in a statement.
Immigrants who wish to join the U.S. military fall into three categories: legal permanent U.S. residents, commonly known as "green card" holders; foreign-born recruits with key medical or language skills who came to the United States under student, work or asylum visas and enlisted through MAVNI; and special status non-immigrant enlistees, who are residents of the Federated States of Micronesia, Republic of the Marshall Islands, and Palau.
The Trump administration in 2017 announced major changes to the way the Pentagon would vet and clear foreign-born recruits and other overall changes to when a service member would qualify for naturalization.
The impact was felt across all three categories of recruits, said retired Army Reserve Lt. Col. Margaret Stock, an attorney who specializes in representing immigrant soldiers in her private practice.
Immigrant enlistees previously could join basic training once a background investigation had been initiated, and they could become eligible to start seeking citizenship after one day of military service. Under the new policy, enlistees do not go to basic training until their background investigation is complete, and they have to complete basic training and 180 days of service before they can seek citizenship.
In the months that followed, the Defense Department shut down naturalization offices at some of its basic training locations, citing the new policy.
Other changes appeared procedural but had deep impact, such as the change that only higher-ranking officers, at colonel or above, were authorized to sign key USCIS forms verifying that an enlistee had served honorably. The signatures had to be original, too, which made it much more difficult for troops in outlier areas where the nearest colonel or higher-ranking officer may be hundreds of miles away, Stock said.
The new rules had a chilling effect, military immigration attorneys said. Unit leaders who previously would have shepherded naturalization paperwork through for their service members have stopped doing so, the attorneys said.
"People are telling them 'wait until you get to your first unit.' When they get to the unit they are told, 'we don't know anything about this anymore,'" Stock said.