President Obama plans to overhaul the Joint Chiefs of Staff this year as he seeks to replace a handful of longtime members whose terms are coming to a close. Obama on Tuesday nominated Marine Gen. Joseph Dunford, commandant of the Marine Corps, to succeed Army Gen. Martin Dempsey as chairman this fall. He also tapped Air Force Gen. Paul Selva, head of U.S. Transportation Command, to replace Navy Adm. James “Sandy” Winnefeld as vice chairman. In the roles since 2011, Dempsey and Winnefeld are expected to retire after their current two-year terms end in October and August, respectively. What’s more,...