National Defense Area

National Defense Areas (NDAs) are military installations designated by the second Trump administration at the Mexico–United States border which are operated by the US Department of Defense, where troops can search and detain.^{[1][2][3][4][5][6][7][8]}

Joint Task Force-Southern Border assumed control of the southern border mission from Joint Task Force North on March 14, 2025. The southern border mission is supported by thousands of service members as part of the expanded role of the pentagon in the Trump administrations border priorities.^[9][10][11]

The creation of these NDAs was outlined in a National Security Presidential Memorandum (NSPM-4)^[12] issued on April 11, 2025, titled "Military Mission for Sealing the Southern Border of the United States and Repelling Invasions." The memorandum provides for the DOD to take jurisdiction over lands reasonably necessary to enable military activities, including border-barrier construction and emplacement of detection and monitoring equipment to implement Executive Order 14167.^[13]

The first zone, the New Mexico National Defense Area as part of Fort Huachuca.^[14][15][16] A second National Defense Area, The Texas National Defense Area (TXNDA), was announced as part of Fort Bliss.^{[17][18][19][20][21]} NDA 3 covering approximately 250 miles of the Rio Grande River in Cameron and Hidalgo County, Texas was announced which will be administered as part of Joint Base San Antonio.^{[22][23][24][25]} In February 2026, the U.S. Air Force announced that they would be adding an additional 40 miles from the end of NDA 3 to Roma, Texas extending the NDA.^[25] NDA 4 was established as part of Marine Corps Air Station Yuma.^{[26][27][28][29][30]} In December 2025, the Interior Department announced it would transfer roughly 760 acres of public land in San Diego County and Imperial County.^[31][32] The Air Force also added NDA 6 running from Falcon Dam to Del Rio and it would also be administered by Joint Base San Antonio.^[25]

The establishment of NDAs is authorized under existing laws, specifically 50 U.S.C. § 797 and 18 U.S.C. § 1382. These laws allow military personnel to remove trespassers from military installations. In May 2025, Federal judge Gregory B. Wormuth dismissed charges against 100 people on account that "migrants couldn’t know they were trespassing".^[33][34]

"More than 1,400 migrants have been charged with trespassing on military territory".^[35]

Border communities have been impacted by the NDAs.^[36]

In January 2026, military units in NDA 3 began using Seasats Lightfish autonomous surface vehicles to monitor border crossings.^[25]