President Trump picked Lt. Gen. H.R. McMaster, a widely respected military strategist, as his new national security adviser on Monday, calling him “a man of tremendous talent and tremendous experience.” McMaster replaces Michael Flynn, who was asked to resign by Trump last week. Flynn misled Vice President Mike Pence over his conversations with the Russian ambassador to the US, in which the two discussed election-related sanctions imposed on Russia during their phone call that took place before Trump took office.