Non-citizen veterans of military service may be subject to removal for a variety of reasons, including the commission of crimes worthy of imprisonment, engagement in terrorist activities, and failure to comply with visa requirements. Even nonviolent and misdemeanor crimes can result in mandatory deportation and lifetimes bars to reentry and naturalization in the U.S. In a 2024 article by the Military Times, about 94,000 veterans do not possess U.S. citizenship and are at risk of deportation.[1] For crimes that may result in a non-citizen being removed (deported), a thorough discussion can be found at: nolo.com/legal-encyclopedia/crimes-that-will-make-immigrant-deportable.html
[1] See: militarytimes.com/news/your-military/2024/04/15/deported-veterans-struggle-to-access-va-services-study-finds