“Next week ICE will begin the process of removing the millions of illegal aliens who have illicitly found their way into the United States,” Trump wrote, referring to U.S. Immigration and Customs Enforcement. “They will be removed as fast as they come in.”

Large-scale ICE enforcement operations are typically kept secret to avoid tipping off targets. In 2018, Trump and other senior officials threatened the mayor of Oakland, Calif., with criminal prosecution for alerting city residents that immigration raids were in the works…

In April, acting ICE director Ronald Vitiello and Homeland Security Secretary Kirstjen Nielsen were ousted after they hesitated to go forward with the plan, expressing concerns about its preparation, effectiveness and the risk of public outrage from images of migrant children being taken into custody or separated from their families…

U.S. officials with knowledge of the preparations have said in recent days that the operation was not imminent, and ICE officials said late Monday night that they were not aware that the president planned to divulge their enforcement plans on Twitter.