Use of the term grey-zone is widespread in national security circles, but there is no universal agreement on the definition of grey-zone, or even whether it is a useful term, with views about the term ranging from "faddish" or "vague", to "useful" or "brilliant".
The grey-zone is defined as "competitive interactions among and within state and non-state actors that fall between the traditional war and peace duality" by the United States Special Operations Command. A key element of operations within the grey-zone is that they remain below the threshold of an attack which could have a legitimate conventional military response (jus ad bellum). One paper defined it as "coercive statecraft actions short of war", and a "mainly non-military domain of human activity in which states use national resources to deliberately coerce other states". The Center for Strategic and International Studies defines the grey-zone as "the contested arena somewhere between routine statecraft and open warfare." British Defence Secretary Ben Wallace called the grey-zone "that limbo land between peace and war."
According to Vincent Cable, examples of grey-zone activities include undermining industrial value chains or oil and gas supplies, money laundering, and the use of espionage and sabotage. According to Lee Hsi-ming "gray zone conflict is characterized by using the threat of force to create fear and intimidation."
The concept of the grey-zone is built on existing military strategies; however, information technology has created radical new spaces which have expanded what is possible. Modern hybrid warfare and political warfare operations primarily occur in the grey-zone.
In the late 2010s, China escalated to grey-zone warfare with Taiwan in an attempt to force unification with the smaller country. Taiwan's Coast Guard Administration has had to expand rapidly to meet the rising grey-zone challenge. China's grey-zone operations against Taiwan in the maritime domain are meant to establish presence while maintaining plausible deniability.
It is generally believed that non-democratic states can operate more effectively in the grey-zone as they are much less limited by domestic law and regulation. It can also be very hard for democratic states to respond to grey-zone threats because their legal and military systems are geared towards seeing conflicts through the sense of war and peace with little preparation or consideration for anything in between. This can lead democratic states to either dramatically overreact or under-react when faced with a grey-zone challenge.
Relation with hybrid warfare
The concept of grey-zone conflicts or warfare is distinct from the concept of hybrid warfare, although the two are intimately linked as in the modern era states most often apply unconventional tools and hybrid techniques in the grey-zone. However, both concepts of ‘hybrid war’ and ‘grey zones’ strategies are built around the idea of the existence of some intermediate state between (negative) peace and international as well as non-international armed conflict. Many of the unconventional tools used by states in the grey-zone such as propaganda campaigns, economic pressure and the use of non-state entities do not cross over the threshold into formalized state-level aggression.
- Dobbs, Thomas; Fallon, Garth; Fouhy, Sarah (9 September 2020). Grey Zone. The Forge (Report). Australian Defence College. Retrieved 18 March 2022.
- Kapusta, Philip. "The Gray Zone" (PDF). www.soc.mil. United States Special Operations Command. Retrieved 18 February 2021.
- "Challenging the Grey Zone". www.law.upenn.edu. University of Pennsylvania Law School. Retrieved 18 February 2021.
- Morris, Lyle J.; Mazarr, Michael J.; Hornung, Jeffrey W.; Pezard, Stephanie; Binnendijk, Anika; Kepe, Marta. "Gaining Competitive Advantage in the Gray Zone" (PDF). www.rand.org. RAND. Retrieved 18 February 2021.
- Schaus, John; Federici, Joseph; Sheppard, Lindsey. "Gray Zone Project". www.csis.org. CSIS. Retrieved 24 February 2021.
- Nicholls, Dominic. "SAS ordered to start disrupting Russian meddling around the world". news.yahoo.com. The Telegraph. Retrieved 21 March 2021.
- Korolev, Alexander (2023). "Political and Economic Security in Eurasia: English School Perspective". China and Eurasian powers in a Multipolar World Order 2.0: Security, Diplomacy, Economy and Cyberspace. Mher Sahakyan. New York: Routledge. p. 11. ISBN 978-1-003-35258-7. OCLC 1353290533.
- Su-wei, Wu; Chin, Jonathan. "Embrace innovation, admiral says". taipeitimes.com. Taipei Times. Retrieved 17 June 2023.
- Dowse, Andrew; Bachmann, Sascha-Dominik. "Explainer: what is 'hybrid warfare' and what is meant by the 'grey zone'?". theconversation.com. The Conversation. Retrieved 24 February 2021.
- LEE, YIMOU; LAGUE, DAVID; BLANCHARD, BEN. "China launches 'gray-zone' warfare to subdue Taiwan". www.reuters.com. Reuters. Retrieved 18 February 2021.
- Chien-pang, Liu; Kui-hsiang, Wen; Lim, Emerson. "Taiwan coast guard ships add new livery to distinguish them from China's". focustaiwan.tw. Focus Taiwan. Retrieved 17 February 2021.
- Chan, Eric (2 June 2021). "Escalating Clarity without Fighting: Countering Gray Zone Warfare against Taiwan (Part 2)". globaltaiwan.org. The Global Taiwan Institute. Retrieved 21 June 2021.
- Belo, Dani; Carment, David. "Grey-Zone Conflict: Implications for Conflict Management". www.cgai.ca. CGAI. Retrieved 24 February 2021.
- Stoker, Donald; Whiteside, Craig (Winter 2020). "Blurred Lines: Gray-Zone Conflflict and Hybrid War—Two Failures of American Strategic Thinking". Naval War College Review. 73 (1): 1–37.
- Carment, David; Belo, Dani. "Gray-zone Conflict Management: Theory, Evidence, and Challenges". www.airuniversity.af.edu. Air Force University. Retrieved 18 February 2021.
- Kormych, Borys; Malyarenko, Tetyana; Wittke, Cindy (2023). "Rescaling the legal dimensions of grey zones: Evidence from Ukraine". Global Policy. 14 (3): 516–530. doi:10.1111/1758-5899.13233. ISSN 1758-5880.