A Republican congressman who served alongside the National Guard on the U.S.-Mexico border this month is warning that the decision by some states to remove guardsmen will lead to a new wave of illegal immigration that will be “massive” in scale.

Illinois Rep. Adam Kinzinger, a lieutenant colonel and pilot in Wisconsin’s National Guard, said fewer troops in border states will prompt more migrants who might have applied for asylum at ports of entry or in their home country to instead pay cartels to get them into the United States. He warned that reducing border troops will make it easier for cartels to smuggle them through.