Elon Musk’s war on MAGA has quickly gone nuclear after the billionaire CEO blasted a social media user’s comments about HB1 visas Friday, and former Trump chief strategist Steve Bannon called him a “toddler” for his response.

Less than a month before Donald Trump returns to office, two of his most ardent allies have plunged into a fierce online debate over immigration, specifically the government’s visa program that allows American companies to hire so-called “highly skilled” foreign workers.