The Justice Department on Thursday sued Illinois and Chicago, accusing the state and city of impeding the Trump administration’s immigration efforts with so-called “sanctuary city” laws, as the U.S. carries out what President Donald Trump said would be the “largest deportation operation” in its history.

President Donald Trump has promised a massive wave of deportations under his administration, but attorneys, judges and others who are deeply embedded in U.S. immigration courts warn an influx of new cases could crush an already strained system.

Military planes are being used for deportations to expedite the process quickly and efficiently, with little concern for costs, as part of Donald Trump's national emergency on illegal immigration.