When Anti-Access/Area Denial (A2/AD) is discussed in the United States, it is typically in offensive terms. Conceptually, the aim of A2/AD is to array a constellation of systems, such as long-range sensors, cruise missiles, and even conventional theater ballistic missiles to prevent an adversary use of an area or domain, and deny them freedom of action. For a hypothetical conflict in the Pacific, the common frame is of forward, proactive U.S. forces beset by Chinese A2/AD systems intent on denying U.S. ships and aircraft use of the waters and airspace inside the first island chain, the string of islands stretching from Japan south to the Philippines that encircles China from the sea, and even threatening forces as far away as the second island chain, like U.S. bases on Guam. The idea of a U.S. A2/AD umbrella is rarely considered, but the U.S. Army is working to build a future capability to achieve just that via its ‘Multi-Domain Battle’ concept.
A panel at the recent Association of the U.S. Army conference described Multi-Domain Battle (MDB) as a hyper-joint Army that will both operate in, and affect all other domains in conjunction with the other services. This translates to using land maneuver—i.e. ground forces—to both exploit and enable operations across air, sea, cyber, space, and the electro-magnetic spectrum. The Army does not use the (now out of favor) term A2/AD to describe the MDB concept, nor see it as a mirror A2/AD umbrella. Instead, the concept is framed offensively as a counter to an adversary A2/AD umbrella; one of MDB’s stated purposes is to “overcome enemy anti-access and area denial.”
Examples of A2/AD-defeating MDB capabilities could include: cyber intrusions to disrupt an enemy anti-aircraft battery to permit local air cover for ground force movement; ground forces disabling enemy anti-air or ground-based anti-ship batteries for the air force and navy; ground forces able to call on new long-range fire support from both air and sea; or army anti-air and missile defense batteries that can defend against anti-access weapons like the Chinese DF-26, a conventional ballistic missile capable of reaching U.S. bases in Japan and Guam. Lieutenant General H.R. McMaster sees the Army’s role against the A2/AD challenge to be a forward and expeditionary force that keeps seams open in the enemy’s defenses for air- and sea-power to exploit – “If you’re already there, it’s not denied space, it’s contested from the beginning.”
But despite this offensive conception for MDB, and whether or not the Army embraces the term, many capabilities it envisions would help project a de facto U.S. A2/AD umbrella more than they would assist in defeating an adversary’s. General McMaster wants to see the army “projecting power outwards from the land.” Undersecretary of the Navy Janine Davidson put it more directly; she wants to “get the Army to sink a ship” and “be a part of sea control,” missions heretofore almost solely the responsibility of the Navy, with some Air Force contributions. The Army is studying the long-range High Velocity Projectile, originally designed for next-generation naval guns, for use from its 155mm mobile artillery and modifying some of its multiple launch rocket systems (MLRS) and missile systems for anti-ship use. USD Davidson would even like to see the Army not only modify its existing systems but one day perhaps field dedicated long-range anti-ship cruise missiles, and be able to conduct a near-simultaneous engagement of an adversary surface ship, cruise missile, and aircraft.
The effect of this land power projected into the sea and air domains is to provide the United States with a credible A2/AD umbrella that it could project from the western Pacific’s first island chain. Scholars and strategists skeptical that outright U.S. primacy over China can be maintained over the long-run have advocated this idea for several years. The idea is similar to former Center for Strategic and Budgetary Analysis’ President Andrew Krepinevich’s suggestion of ‘Archipelagic Defense’ made up of land-based capabilities on the first island chain. Shang-su Wu of Singapore’s S. Rajaratnam School of International Studies suggested a return to the idea of ‘Naval Fortresses’ utilizing missiles and air power as a way for China’s smaller island neighbors to hedge against the possibility of waning U.S. Naval supremacy in the Western Pacific. James Holmes, a professor at the U.S. Naval War College, advocates combining containment capabilities with defensive missile shields to turn the first island chain into a barrier Chinese forces would be unable to break through.
Even though the Army clearly sees Multi-Domain Battle as an enabler of offensive operations, it recognizes the defensive contribution it can make to protect the air and sea domains from adversary A2/AD systems. As a result, a deployable U.S. A2/AD shield can be considered a “lesser included” capability of the broader MDB concept that may provide a robust backstop if mature Chinese A2/AD systems prove too costly to defeat offensively. If these U.S. capabilities are realized, it will bring the Western Pacific closer to the Asian security environment scholars Stephen Biddle and Ivan Oelrich recently envisioned. They see current U.S. “command of the commons” steadily replaced with an environment of competing A2/AD umbrellas resulting in “a U.S. sphere of influence around allied landmasses, a Chinese sphere of influence over the Chinese mainland, and contested battlespace covering much of the South and East China Seas, wherein neither power enjoys wartime freedom of surface or air movement.” That is clearly not the decisive outcome the Army is planning for Multi-Domain Battle to deliver, but it may be the concept’s more likely and robust strategic effect.