Source: The Washington Post     Defense Secretary Jim Mattis submitted a letter Dec. 20 saying he would step down in February. Lawmakers are expressing concerns about his departure. (Video: Sarah Parnass /Photo: Jabin Botsford/The Washington Post) By Paul Sonne, Josh Dawsey and Missy Ryan Defense Secretary Jim Mattis resigned Thursday after clashing with President Trump over … Continue reading Mattis resigns after clash with Trump over troop withdrawal from Syria and Afghanistan