Donald Trump was up late Tuesday night threatening to veto the defense spending bill—unless a requirement in it to rename U.S. military bases that honor Confederate leaders is dropped. The legislation, which funds the nation’s military operations, is widely considered a “must-pass” bill, and is one of the few pieces of legislation that Congress can be counted on to pass each year. However, Trump is now objecting to an amendment by Sen. Elizabeth Warren that proposed bases named in honor of Confederate leaders be renamed as a part of the annual authorization bill. Trump wrote: “I will Veto the Defense Authorization Bill if the Elizabeth ‘Pocahontas’ Warren (of all people!) Amendment, which will lead to the renaming (plus other bad things!) of Fort Bragg, Fort Robert E. Lee, and many other Military Bases from which we won Two World Wars, is in the Bill!” Warren’s amendment to the legislation calls for removing the names of Confederate leaders from all military assets.