The 2025 United States border emergency was declared by President Donald Trump on 20 January 2025 in response to the Mexico-United States border crisis; 2024 alone had resulted in nearly 3 million inadmissible encounters across the country.
Trump declared an emergency on the Southern border on the day of his second inauguration; by 23 January 2025, the Pentagon prepared to deploy 1,000 US Army troops and 500 US Marines to San Diego, California and El Paso, Texas. Four large transport aircraft were prepared for deportation flights. The military personnel would construct physical barriers and gather intelligence on cross-border smuggling operations, while law enforcement would persist in their work to prevent undocumented border crossings. On the same day as the announcement of the impending troop deployment, a judge in Washington blocked an attempt by Trump to revoke birthright citizenship with another executive order.