“Since Washington crossed the Delaware at Christmas in 1776, American troops have missed holidays at home to defend our experiment in democracy,” Mattis said in a 20-second video. “To all you lads and lasses holding the line in 2018, on land, at sea, or in the air, thanks for keeping the faith. Merry Christmas and may God hold you safe,” Mattis concluded. The video was recorded Dec. 19, one day before Mattis submitted his scathing resignation letter