The changing of the guard at the Tomb of the Unknown Soldier in Arlington National Cemetery is one of the many roles of the Army’s Old Guard. The unit conducts more than 6,000 ceremonies each year, including funeral escorts, parades and presidential events. Former Old Guard platoon leader, Sen. Tom Cotton, gives an inside look at the Army’s oldest active-duty regiment in his new book, “Sacred Duty: A Soldier’s Tour at Arlington National Cemetery.” Cotton joins “CBS This Morning” to discuss the book and President Trump’s tariffs on Chinese imports.