DEMPSEY VISIT U.S. Army Gen. Martin E. Dempsey, left, chairman of the Joint Chiefs of Staff, signs the guestbook of Canadian Air Force Gen. Thomas J. Lawson, chief of Canada's defense staff, during his three-day visit to Ottawa, Ontario, April 15, 2014. SHARE: Download: Full Size (0.06 MB) Credit: VIRIN: 040427-E-MKK44-846.jpg Photo Gallery