In most real conflicts the potential escalation sequence is more like
a ladder that has been bent and twisted out of shape with all sorts
of extra and odd protuberances added on, which vitally affect how the
conflict does or does not climb it..... Controlling escalation
will depend crucially on identifying the particular twists and
protuberances of that conflict's misshapen ladder. (1)
Warfare has become even more complicated since Richard Smoke wrote this description of escalation in 1977. The National Security Space Strategy describes space as "congested, contested, and competitive," yet satellites underpin U.S. military and economic power. Activity in cyberspace has permeated every facet of human activity, including U.S. military operations, yet the prospects for effective cyber defenses are bleak. Many other actors depend on continued access to these domains, but not nearly as much as the United States.
For this reason, some analysts argue that China's opening salvo in a conflict with the United States would unfold in space and cyberspace. Worst-case scenario assessments conclude that such an attack might render the United States blind, deaf, and dumb almost exclusively through nonkinetic means, although it is unclear how effective attacks in the space and cyber domains would be in an actual military conflict. How do concepts such as escalation, deterrence, and proportionality apply in such a context? What "odd protuberances" would counterspace and cyber attacks create in an escalation ladder? What are the salient thresholds for cross-domain attacks? And what exactly does cross-domain mean? This paper explores these questions using the illustrative example of a hypothetical U.S.-China conflict because both countries possess diverse strategic capabilities that span air, land, sea, space, and cyberspace.
Defining Cross-domain: Platforms or Effects?
Cross-domain is an ambiguous term. U.S. doctrine identifies land, air, and sea as domains. Recent U.S. national security policy and strategy documents recognize space and cyberspace as distinct domains as well. (2) Assuming that all five are strategic domains, there are at least two different ways an action could cross domains.
Cross-domain could be defined according to the platform from which an actor launches an attack and the platform on which the target resides. Destroying a satellite with a ground-launched antisatellite (ASAT) missile is a cross-domain attack, whereas destroying one with a co-orbital ASAT (for example, a maneuverable satellite) is not. Striking a surface ship with a conventional air-launched cruise missile is a cross-domain attack, whereas an attack on the same target with a sea-launched cruise missile (SLCM) is not. Defining cross-domain by platforms demonstrates that cross-domain operations are not new. Air attacks on naval forces, naval attacks on air forces, and attacks from both domains on ground forces are common in modern warfare. Indeed, in many instances, a cross-domain operation might simply be the most expedient option. As an example, a nation under attack by SLCMs might, for a variety of reasons, be able to attack the adversary's naval assets more quickly with aircraft than with submarines and surface ships.
This definition might be too simplistic. Most U.S. military forces on land, in the air, and at sea make use of cyber and space assets, and most complex missions integrate contributions from multiple domains. One could even argue that a precision conventional strike is a cross-domain attack, regardless of whether the attacking platform and target are in the same domain, if it utilizes satellites and computer networks. By the same reasoning, characterizing a cyber attack--as opposed to cyber exploitation--against U.S. military computer networks as single-domain is misleading. If successful, such an attack would have important cross-domain effects: it would undermine the air, ground, or naval forces that depend on the degraded computer networks. …