Bannon said Musk ― a naturalized U.S. citizen ― “should be deported,” while Musk predicted that Bannon ― who served a four-month sentence for contempt of Congress ― could be heading back to prison for a longer term. Bannon on his “War Room” podcast slammed Musk for saying he would start a new political party, the America Party.

A public feud between President Donald Trump and his on-again, off-again ally, billionaire Elon Musk, reignited this week after an apparent truce lasted less than a month.

Here’s what to know about the history of—and the Trump Administration’s efforts to ramp up—“denaturalization.”