Marines cover their ears as a round is fired from a M198 155mm Medium Howitzer. U.S. Marines cover their ears as a round is fired from a M198 155mm Medium Howitzer during exercise Rim of the Pacific '04 on the Hawaiian Islands, on July 14, 2004. Exercise Rim of the Pacific '04 is an international maritime exercise designed to enhance the tactical proficiency of participating Pacific Rim nations including participants from Australia, Canada, Chile, Japan, South Korea, the United Kingdom, and the U.S. SHARE: Download: Full Size (0.12 MB) Credit: VIRIN: 618952-X-KDE74-526.jpg Photo Gallery