WASHINGTON -- Later this year, Soldiers will initiate five-month extended rotations to countries like Thailand, the Philippines and Papua New Guinea, Secretary of the Army Ryan McCarthy said at the Brookings Institution Friday.The Indo-Pacific region is home to half the world's population -- including several of the world's largest militaries -- so a key to realizing the vision set in the National Defense Strategy is to bolster alliances there, he said.Soldiers will do more than provide a steady security presence with foreign allies though, he said. At this moment, U.S. troops are assisting the Royal Thai Army stand up new Stryker units after that foreign military secured 15 Infantry Carrier Vehicles.The Philippines recently requested help training 72 infantry battalions after they upgraded their equipment, McCarthy said.Additional deployments and exercises in the region are being planned through 2022, he said.ROLE IN THE PACIFIC BEYOND SOUTH KOREAWhen many think of the Army's presence in the Indo-Pacific, they think of troops in South Korea, said Michael O'Hanlon, Brookings Institution director of research, foreign policy. However, there's an increased emphasis in other parts of the combatant command that goes all the way to the India-Pakistan border, he added."Having our forces in the region reinforces the American alternative to the Belt and Road Initiative," McCarthy said, regarding the Chinese government's 2013 global development strategy. "In order to be competitive and gain an advantage, we must have a continuous presence."Allies understand how partnering with the United States means having modern and interoperable equipment, training on a continuous basis, and a commitment that should deterrence fail -- the U.S. is a present partner and the world's best fighting force, McCarthy said."There is an ongoing fight for influence in the region, making our presence critical," McCarthy said. "Partners matter, but the type of partner is paramount."China has a history of coercive economics, and many nations partner with them out of necessity, McCarthy said, adding, "And in this, lies a great deal of vulnerability."Having the U.S. Army in the region -- with its modernized weaponry -- nested alongside allies "changes the calculus and creates dilemmas for potential adversaries," McCarthy said. Having the U.S. Army in the region also strengthens America's position to conduct commerce and compete economically, he added"China may be a partner of necessity," he said, "but the U.S. Army is the partner of choice."MULTI-DOMAIN OPERATIONS IN THE PACIFIC"While we continue to do traditional security cooperation, we are also employing new capabilities and using the Indo-Pacific as grounds to test our new concept -- known as Multi-Domain Operations," McCarthy said.MDO is how the Army -- as part of the joint force -- can counter and defeat a near-peer adversary capable of contesting the U.S. in all domains such as air, land, maritime, space, and cyberspace."Our closest allies and partners have invested more in building similar capabilities as us," McCarthy said. "For example, Japan, Thailand, Singapore all are developing MDO-like concepts in concert with us."MDO task forces are set to train in the Indo-Pacific during the upcoming deployments.The new concept was first tested in the region in 2018, months after the National Defense Strategy was published and changed the Army's focus toward great power competition. The force conducted its first tests then with the Multi-Domain Task Force and Intelligence, Information, Cyber, Electronic Warfare and Space Units -- known as I2CEWS.Then in 2019, the Army tested MDO concepts again with exercises like Orient Shield, where American forces partnered with Japanese forces in the East China Sea. With its headquarters in Japan, the task force elements were distributed across the Senkaku Islands.Since then, the task force has conducted multiple large-scale exercises with more scheduled.Seeking to regain overmatch and a solution for converging all domains, MDO gives an asymmetrical advantage, he said. It sets the conditions in theater, while opening a window for the joint force."The U.S. must maintain overmatch against our adversaries," McCarthy said. "The Army is foundational to the joint force's success in the INDO-PACOM area of responsibility. Our modernization focus -- how we fight, what we fight with, and who we are--is in part, driven by our new challenges and potential adversaries."If we wait until there is a conflict, we are already too late," he said. "We don't need any more gunfights. We don't want anymore… but if they come, we'll be ready."