AFTER A TENURE marked by controversy and a contentious week of Congressional hearings, secretary Kristi Noem is out as head of the Department of Homeland Security.

President Donald Trump announced in a Truth Social post on Thursday that Noem would be replaced by Senator Markwayne Mullin of Oklahoma, a staunch Trump ally and immigration hard-liner. “The current Secretary, Kristi Noem, who has served us well, and has had numerous and spectacular results (especially on the Border!), will be moving to be Special Envoy for The Shield of the Americas, our new Security Initiative in the Western Hemisphere we are announcing on Saturday in Doral, Florida,” Trump wrote. “I thank Kristi for her service at ‘Homeland.’”

DHS did not immediately respond to a request for comment.

The agencies under DHS include Immigration and Customs Enforcement, US Customs and Border Protection, the Cybersecurity and Infrastructure Security Agency, the Federal Emergency Management Agency, US Citizenship and Immigration Services, the US Coast Guard, and others. It’s a sprawling network whose vast responsibilities and rapidly expanding budget have put it at the center of the Trump administration’s radical overhaul of immigration and border policy.