Missouri has sent troops to Arizona to assist with border security.
Four soldiers in Missouri's National Guard and a UH-72 Lakota helicopter deployed Tuesday, according to a statement from Gov. Eric Greitens.
The statement says the soldiers will provide aerial surveillance, and will not directly participate in law enforcement.
In April, President Donald Trump asked the Department of Defense and the Department of Homeland Security to work with state governors to place National Guard troops on the U.S. southern border with Mexico.
That coordination is important, because presidents can't automatically use the military for domestic law enforcement.
Missouri's troops are expected to return mid-summer.