Defense Secretary Jim Mattis pressed Congress to reject the idea of a new Space Force last year because he was concerned about defense budget uncertainty, according to his No. 2 at the Pentagon.

The defense secretary wrote a letter to the House and Senate armed services committees amid a budget fight in Congress saying he opposed adding new bureaucracy. But on Thursday, Mattis offered full-throated support of President Trump’s Space Force and unveiled what he called a “clear-eyed” plan to create it.