WASHINGTON (Reuters) - U.S. Defense Secretary Jim Mattis welcomed the naming of Lieutenant General Herbert Raymond McMaster as the new national security adviser, a Pentagon spokesman said on Tuesday.  U.S. President Donald Trump on Monday named McMaster as his new national security adviser, choosing a military officer known for speaking his mind and challenging his superiors. “Secretary Mattis has known Lieutenant General McMaster since the late 1990s when his book was published and he has great respect for his strategic perspective, his intellectual rigor and his managerial discipline,” Pentagon spokesman Captain Jeff Davis told reporters on Tuesday. 
Mattis welcomes naming of Trump's top security adviser: Pentagon