The US Citizenship and Immigration Services (USCIS) dropped an opaque and confusing policy change affecting the citizenship of some children of US government employees and service members born abroad on Wednesday. USCIS estimated on Thursday that 20 to 25 children a year would be affected.

The Department of Defense appears to have been blindsided by the policy change, as it has struggled to provide clarity to an update that will affect a small number of US military personnel serving their country abroad.

USCIS, which explained that this is an effort to bring agency policy in line with those of the Department of State, clarified that about two dozen families may be affected each year.

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It took hours for the Department of Defense to address a policy change regarding citizenship rules for some children born to US troops or government employees born abroad, and it appears they were caught off guard by the new US Citizenship and Immigration Services policy.

"The policy change from the agency, which is part of the Department of Homeland Security, infuriated many at the Pentagon and confused others in the military community," The New York Times reported, noting that some members of this community said the policy called into question the Trump administration's support for the military.

Amid confusion and outrage over the policy update, the Pentagon struggled to provide clear answers to inquiries. "We are just learning of this change, so don't have any information right away about how this impacts our Airmen," an Air Force source told Air Force Magazine editor Rachel Cohen Wednesday immediately after the policy was released. USCIS later clarified that the changes would affect only about two dozen troops a year.

Insider reached out to the Army and Navy for comment but was directed to the Office of the Secretary of Defense, which responded roughly five hours after the USCIS policy became public, saying only that "DoD has been working closely with our colleagues at DHS/USCIS regarding recent policy changes and understands the estimated impact of this particular change is small."

"We are committed to ensuring affected families are provided the appropriate information, resources, and support during this transition," the office spokesperson added.

USCIS, which explained that this is an effort to bring agency policy in line with those of the Department of State, clarified that about two dozen families may be affected each year.

The changes primarily affect two groups of government employees:

US citizens who adopt a foreign born child while serving abroad must establish their legal residency via official orders before getting a citizenship certificate.

Green card holders serving in the US military who give birth abroad must now file a form to establish permanent legal residence.

The policy change, which impacts some noncitizens serving in the US military, was handed down abruptly, but in tandem with other striking changes to immigration policy, including a policy protecting migrants receiving medical care in the US.

According to USCIS Acting Director Ken Cuccinelli, the memo signified little change in actual policy. But concern over the opaque language and lack of clarity surrounding which service members and government employees would be affected — and in what contexts — was palpable Wednesday evening.

The new policy is set to take effect October 29, 2019.