As I've said, I think the Army should plan for major operations in Asia to oppose China (as I outlined in Military Review):
In any future emerging confrontation in the Asia Pacific, the U.S. Army eventually will have to take a pivotal role in order for the United States to prevail. Therefore, the U.S. Army must consider and prepare for a role in the Asia-Pacific region that goes beyond merely fighting anti-access/area denial (A2/AD) threats to the Navy to one that better accounts for the value of large-scale land operations in support of a joint campaign.
The main thrust is that the Army could operate alongside allied Asian armies around China that are opposing China--not that we should invade China to conquer it. India, Thailand, Vietnam, Taiwan, South Korea, and Japan come to mind.
And Russia comes into this, too, given that its territory reaches the Pacific. Either as an enemy or even (if the Russians get their collective head out of their collective butt) as a potential ally against Chinese aggression.
Remember, China has modernized its country--especially the coastal regions where the Army might operate--and is modernizing the PLA:
Many of the focus areas of the current (11th) round of reforms, such as strengthening the PLA’s ability to conduct joint operations and rebalancing the military’s composition from the ground forces to the naval, air, and missile forces, were conceived in the 1980s and 1990s. This agenda followed changes to Chinese military strategy to focus less on preparing for a general war with the Soviet Union or the United States—which had driven China’s defense planning during the Cold War—and more on a smaller scale conflict around China’s borders. Key events signaling the need for reform included the 1990–1991 Gulf War, which showcased the U.S. military’s advantages in doctrine and technology, and the 1995–1996 Taiwan Strait crisis, which exposed the PLA’s inability to deter Taiwan independence forces or counter U.S. intervention on Taipei’s behalf.
The Chinese army is no longer a mass infantry force that can fight conventionally and as irregulars and guerrillas that acts like a sponge to absorb and entangle an invading force. This change makes the Chinese army more formidable in battle. But it also can provide opportunities. If China thinks it only has to fight smaller wars around their periphery, 10-20 American maneuver brigades/regiments (Army and Marine Corps) will complicate their options, no?
So I do not rule out operations on the mainland of China. One opportunity would be if the Army was supporting a major force inside China. This is most like my basic notion that supporting another country's army could be a mission.
But in that case, it would be a Chinese army in a "China" that has become a geographic term rather than a unified state/empire.
But there are other possibilities, too. American troops participated in the multi-national mission to Peking in the Boxer Rebellion. Although in this case the mission was enabled by China not being a fully functioning state even though it was formally unified.
Along those lines, maybe that situation is replicated on Hainan Island. Perhaps a multi-national force built around an American Army-Marine force is used to capture that physically separated base area in order to reduce the ability of China to project power into the South China Sea.Looming over Vietnam, Hanoi might contribute ground forces to that mission if we--or allies with shipping--help lift them.
In the MR article linked I mentioned the possibility of operations on the mainland for short periods to achieve specific missions. Perhaps a Marine-Army operation to establish missile and air bases on the mainland is needed to help the Navy and Air Force establish control in the waters off of China for a mission they need to achieve.
Another mission could be raids. They could be small and of short duration, like the "shoot and scoot" artillery raids we conducted against Iraqi forces occupying Kuwait before we liberated the country in 1991 during the Persian Gulf War (noted here). But depending on busy the Chinese army is with other threats around their periphery (and how busy the People's Armed Police semi-army is), a very large Thunder Run by Task Force 1-64 (which tested my pre-war desire to "bounce" Baghdad on the run rather than besiege the city) on a corps level--a Dragon Run--might be carried out to replicate Sherman's march to the sea in the American Civil War:
Sherman's March to the Sea (also known as the Savannah Campaign or simply Sherman's March) was a military campaign of the American Civil War conducted through Georgia from November 15 until December 21, 1864, by Maj. Gen. William Tecumseh Sherman of the Union Army. The campaign began with Sherman's troops leaving the captured city of Atlanta on November 15 and ended with the capture of the port of Savannah on December 21. His forces followed a "scorched earth" policy, destroying military targets as well as industry, infrastructure, and civilian property and disrupting the Confederacy's economy and transportation networks. The operation broke the back of the Confederacy and helped lead to its eventual surrender. Sherman's bold move of operating deep within enemy territory and without supply lines is considered to be one of the major achievements of the war and is also considered to be an early example of modern total war.
If the Marines land and allow an Army corps built around 6 maneuver brigades (plus the usual supporting units including engineers) to rampage through the more prosperous part of China, real damage to China's civilian and military infrastructure could be inflicted. And Chinese morale could take a hit.
As the Army corps marches off inland, the Marines could--while providing air support and aerial logistics support along with the Air Force while they remain ashore--prepare to debark and/or move along the coast to capture a port on the coast where the Army force will eventually reach and disembark behind a shield of Marines holding the perimeter.
Obviously, the point of embarkation should be taken based on opportunities for avoiding Chinese opposition during the Dragon Run. Telegraphing the end point by selecting and seizing a port early will simplify Chinese reactions that could trap the force. Unless an early port seizure is designed to provide one option while also having a staging area to seize the actual port to be used.
Of course, such a mission takes place after the Navy has achieved control of the seas off of a portion of China where the Dragon Run takes place. Navy air support and logistics missions for key items would be needed during the Dragon Run.
Mind you, a Dragon Run might never make sense in the real world should we and the Chinese ef up and go to war with each other.
But I throw it out as an idea to get people thinking about how the Army can contribute a core competency to a war in Asia, rather than thinking all the Army can do is be a naval auxiliary supplying anti-ship and anti-aircraft weapons to support the Navy battle for control of the seas.
Hopefully, if the Chinese see that more of America's military power can be focused on China, deterrence will be improved and nobody will ef up and go to war.