U.S. Army Gen. Martin E. Dempsey, chairman of the Joint Chiefs of Staff, center, and U.S. Ambassador to Brazil Thomas A. Shannon, left, walk to bi-lateral meetings between U.S. and Brazilian leaders in Brasilia, Brazil, March 29, 2012. U.S. Army Gen. Martin E. Dempsey, chairman of the Joint Chiefs of Staff, center, and U.S. Ambassador to Brazil Thomas A. Shannon, left, walk to bi-lateral meetings between U.S. and Brazilian leaders in Brasilia, Brazil, March 29, 2012. SHARE: Download: Full Size (0.69 MB) Tags: Photo Essays Credit: VIRIN: 575569-D-ZUS36-182.jpg Photo Gallery