President-elect Donald Trump’s incoming border czar vows that the biggest city in the Midwest will be “ground zero” for mass deportations, and officials across the political spectrum in Chicago are bracing for a showdown.

Trump campaigned largely on the issue of immigration, promising to carry out mass deportations of roughly 11 million illegal immigrants currently in the U.S.

Local immigration advocates continue preparing for potential mass deportation efforts that could reportedly start as soon as Tuesday.

Immigration czar Tom Homan said Monday that Immigrations and Customs Enforcement had “pulled back” a reported Chicago operation, after news of the potential plan leaked over the weekend, but that Americans will see the agency in action “real soon.