WASHINGTON (Reuters) -U.S. Defense Secretary Pete Hegseth has ordered the removal of half of the 4,000 National Guard troops who had been sent to Los Angeles to protect federal property and personnel during a spate of protests last month, the Pentagon said on Tuesday.

Pentagon spokesperson Sean Parnell said the decision was due to the success of the mission.

"Thanks to our troops who stepped up to answer the call, the lawlessness in Los Angeles is subsiding," Parnell said in a statement. 

"As such, the Secretary has ordered the release of 2,000 California National Guardsmen from the federal protection mission," he added.

President Donald Trump deployed the California National Guard troops to Los Angeles in June, against the wishes of Democratic Governor Gavin Newsom, to quell protests triggered by immigration raids on workplaces by Immigration and Customs Enforcement agents.

He also sent about 700 Marines.

Despite legal challenges, a U.S. appeals court let Trump retain control of California's National Guard. 

But his decision to send troops into Los Angeles prompted a national debate about the use of the military on U.S. soil and inflamed political tension in the country's second-most-populous city. The Pentagon has defended the deployment, saying safeguarding ICE agents ensures they can do their jobs.

Even after the withdrawal of those military personnel from Los Angeles, 2,000 National Guard troops will remain in the city along with the roughly 700 Marines.

Los Angeles Mayor Karen Bass, who has complained that military force was unnecessary and damaging to the local economy, said popular opposition contributed to the withdrawal.

Protesters regularly appear at immigration raids in the Los Angeles area, demonstrating their opposition to the government's display of force.

"This happened because the people of Los Angeles stood united and stood strong. We organized peaceful protests, we came together at rallies, we took the Trump administration to court - all of this led to today's retreat," Bass said.

She referred to a lawsuit the city joined that led to an order from a federal judge barring immigration officers from detaining people based solely on their race or for speaking Spanish.

The troops in Los Angeles are authorized to detain people who pose a threat to federal personnel or property, but only until police can arrest them. Military officials are not allowed to carry out arrests themselves.

Trump has vowed to deport millions of people in the country illegally and has executed raids at work sites including farms that were largely exempted from enforcement during his first term. The administration has faced dozens of lawsuits across the country challenging its tactics.

Trump has increasingly turned to the military in his immigration crackdown.

In addition to sending troops to Los Angeles, thousands of active duty troops have been deployed to the border with Mexico and the Pentagon has created military zones in the border area.

The zones are intended to allow the Trump administration to use troops to detain migrants without invoking the 1807 Insurrection Act that empowers a president to deploy the U.S. military to suppress events such as civil disorder.

During a chaotic raid and resulting protests last week at two sites of a cannabis farm in Southern California, 319 people in the U.S. illegally were detained and federal officers encountered 14 migrant minors, Department of Homeland Security chief Kristi Noem said.

Immigration and Customs Enforcement agents accompanied by National Guard troops in military-style vehicles turned up at two locations operated by Glass House Farms - one in the Santa Barbara County town of Carpinteria, about 90 miles (145 km)northwest of Los Angeles, and one in the Ventura County community of Camarillo, about 50 miles from L.A.

(Reporting by Idrees Ali and Phil Stewart; Editing by Chris Reese, Richard Chang and Michael Perry)

By Idrees Ali and Phil Stewart