National Guard troops helped with the arrest of 23,034 illegal immigrants and the seizure of more than 35,000 pounds of drugs in the roughly six months they were deployed to the border in fiscal 2018, according to U.S. Customs and Border Protection.

The more than 23,000 people arrested were "deportable" noncitizens, DHS said. The operation, dubbed "Guardian Support," also led federal law enforcement to more than 6,100 people who were later turned back, the data said.

Because guardsmen are military personnel and not law enforcement officers, they cannot apprehend people. CBP officers and Border Patrol agents apprehended thousands as a result of guardsmen who were monitoring cameras, flying helicopters, and piloting planes.

Troops are providing support from the air, surveillance backup, and assistance with infrastructure projects such as vegetation clearing and road maintenance, not including border wall construction. Guardsmen can also be used to free up agents to leave their desks and get back out to the field.

The troops monitoring remote video surveillance systems have then been able to report sightings to a greater field of agents, and thus the number of apprehensions has increased, officials have said.

Marijuana accounted for the vast majority of the drugs seized with the aid of National Guard troops, more than 34,600 pounds. But they also helped seize 526 pounds of methamphetamine, 47 pounds of heroin, and 18 pounds of cocaine.

President Trump authorized the deployment last April following the emergence of a caravan of Central American migrants headed to the southern border.

A little more than 2,100 remain deployed, but that number has already started to drop and will continue to drop in the coming weeks as blue states pull out from the mission, according to Pentagon officials.

The mission was renewed through Sept. 30, the end of fiscal 2019. Previous administrations, including the George W. Bush and Barack Obama White Houses, have ordered the National Guard to the southern border to improve border security.