Howitzer Boom U.S. Marines with Marine Rotational Force Darwin fire a howitzer during Exercise Koolendong at Mount Bundey Training Area, Australia, Aug. 26, 2019. Koolendong is designed to increase teamwork between U.S. Marines and the Australian Defence Force. SHARE IMAGE: Download Image: Full Size (1.31 MB) Photo By: Marine Corps Lance Cpl. Nicholas Filca VIRIN: 190826-M-SK440-002D.JPG Photo Gallery