KEKAHA, Hawaii -- "Attention in the TAC! Target is Colorado."The U.S. Army's Multi-Domain Task Force Tactical Command Post, or MDTF TAC, operating at the Pacific Missile Range Facility here is filled with energy and tension.Sweat drips down the faces of the MDTF Soldiers as they process the fire mission, "Colorado," to the 17th Field Artillery Brigade's High Mobility Artillery Rocket System, or HIMARS, crews. Positioned quietly, the Soldiers eagerly await the loud, booming sound of the Japan Ground Self-Defense Force firing of a surface-to-ship missile alongside the HIMARS.The long-range artillery systems fire … then comes silence. Soldiers crowd around the television screen in the TAC as they watch the feed provided by the 25th Combat Aviation Brigade's unmanned aerial system, an MQ-1C Gray Eagle, to see if the round will impact the target. The target is a decommissioned naval vessel also known as ex-USS Racine … it's a good hit!The 17th Field Artillery Brigade, alongside the Japan Ground Self-Defense Force, conducted its first live-fire exercise here, July 12, during the biennial Rim of the Pacific, or RIMPAC, exercise.The Naval Strike Missile was the first to launch as a land-based asset. Following the missile, Apache AH-64E helicopters, assigned to the 25th Combat Aviation Brigade and 16th Combat Aviation Brigade, fired upon the ex-USS Racine. Lastly, two surface-to-ship missiles from the Japan Ground Self-Defense Force launched missiles in conjunction with the 17th Field Artillery Brigade HIMARS system."People are wondering why are we participating in RIMPAC," said U.S. Army Col. Chris Wendland, commander of the 17th Field Artillery Brigade and MDTF. "We are here to support the Navy and our other services, to show them what the U.S. Army's MDTF can provide to the fight."RIMPAC is the world's largest international maritime exercise. It features 25 nations and is typically focused on naval operations. This year, however, U.S. Army ground forces had a role in the exercise for the first time as the MDTF."We are an asset the Navy and our joint services can utilize," said Wendland. "What our maritime adversaries conducting this exercise are looking for are other ships or submarines as threats. What they are not looking for is the Multi-Domain Task Force, our ground forces, who can acquire the target and fire upon it using land-based surface-to-ship missiles, then be able to move freely."U.S. Army Pacific designated the 17th Field Artillery Brigade, a subordinate unit under America's I Corps at Joint Base Lewis-McChord near Tacoma, Washington, as the pilot program for the MDTF concept."We looked across the U.S. Army and selected the best assets and leaders to build an organization that can fight in all domains," said U.S. Army Gen. Robert Brown, commander of U.S. Army Pacific, during a brief to senior leaders before the live-fire event.The concept of MDTF brings together various capabilities to address peer- or near-peer threats that could deny access to U.S. and coalition forces in maritime, land, air, and space domains. The MDTF integrates its assets to overcome adversary anti-access and air-denial through integration and synchronization of a variety of capabilities. These capabilities include unmanned surveillance assets, aviation, long-range artillery, air defense, electronic warfare, cyber, and space assets."We want to leverage and learn what our joint services utilize, as well as integrate our capabilities as a Multi-Domain Task Force into their planning efforts," explained Wendland. "Our goal is to create joint interoperability to be able to deter our adversaries across all domains."RIMPAC has provided the MDTF and the U.S. Army with many "first" opportunities. This is the first time the 17th Field Artillery Brigade has worked under a naval commander instead of providing long-range artillery for I Corps during a military exercise; the first flight for 25th Combat Aviation Brigade's MQ-1C Gray Eagle in Hawaii as a capability of the MDTF; and the first time using a distributed line-of-sight battle management network, knows as Link 16, with joint forces outside of the brigade.The exercise is a tough, realistic training for joint and combined forces to deter and defeat aggression by major powers across all domains and levels of conflict in order to build multi domain concepts.The 17th Field Artillery Brigade will continue to improve multi-domain concepts within the next year as it executes military exercises in Guam and Japan as the pilot program of the U.S. Army's MDTF.Twenty-five nations, 46 ships, five submarines, and about 200 aircraft and 25,000 personnel are participating in RIMPAC from June 27 to Aug. 2 in and around the Hawaiian Islands and Southern California. The world's largest international maritime exercise, RIMPAC provides a unique training opportunity while fostering and sustaining cooperative relationships among participants critical to ensuring the safety of sea lanes and security of the world's oceans. RIMPAC 2018 is the 26th exercise in the series that began in 1971.