HO CHI MINH CITY, Vietnam – Amid speculation that he soon might be replaced, Defense Secretary Jim Mattis said President Donald Trump told him he supports the retired Marine general “100 percent.” The assertion comes only days after Trump mused on national television about Mattis leaving his post. Mattis said Trump gave him this assurance during a phone call while Mattis was flying from Washington to Ho Chi Minh City, Vietnam, on Tuesday.