An undeclared war is a

military conflict War is an armed conflict between the armed forces of states, or between governmental forces and armed groups that are organized under a certain command structure and have the capacity to sustain military operations, or between such organize ...

between two or more nations without either side issuing a formal

declaration of war A declaration of war is a formal act by which one state announces existing or impending war activity against another. The declaration is a performative speech act (or the public signing of a document) by an authorized party of a national gov ...

. The term is sometimes used to include any disagreement or conflict fought about without an official declaration. Since the

United Nations The United Nations (UN) is the Earth, global intergovernmental organization established by the signing of the Charter of the United Nations, UN Charter on 26 June 1945 with the stated purpose of maintaining international peace and internationa ...

police action In security studies and international relations, a police action is a military action undertaken without a formal declaration of war. In the 21st century, the term has been largely supplanted by " counter-insurgency". Since World War II, formal ...

in the

Korean War The Korean War (25 June 1950 – 27 July 1953) was an armed conflict on the Korean Peninsula fought between North Korea (Democratic People's Republic of Korea; DPRK) and South Korea (Republic of Korea; ROK) and their allies. North Korea was s ...

, some governments have pursued disciplinary actions and limited warfare by characterizing them as something else such as a military action or armed response. Under

customary international law Customary international law consists of international legal obligations arising from established or usual international practices, which are less formal customary expectations of behavior often unwritten as opposed to formal written treaties or c ...

, it is not necessary to declare war—simply beginning hostilities is sufficient to make belligerent intentions clear.

United States

There is no specific format required under United States law for the way an official war declaration will be structured or delivered. The United States Constitution states: "The Congress shall have Power ��To

declare War A declaration of war is a formal act by which one state announces existing or impending war activity against another. The declaration is a performative speech act (or the public signing of a document) by an authorized party of a national gover ...

, grant Letters of Marque and Reprisal, and make Rules concerning Captures on Land and Water". As of September 2024, the

United States Congress The United States Congress is the legislature, legislative branch of the federal government of the United States. It is a Bicameralism, bicameral legislature, including a Lower house, lower body, the United States House of Representatives, ...

has formally declared war 11 times, and has not done so since 1942; 6 of these were WWII declarations. The United States did not declare war during its involvement in Vietnam, although the

Gulf of Tonkin Resolution The Gulf of Tonkin Resolution or the Southeast Asia Resolution, , was a joint resolution that the United States Congress passed on August 7, 1964, in response to the Gulf of Tonkin incident. It is of historic significance because it gave U.S. ...

authorized the escalation and use of military force in the Vietnam War without a formal declaration of war. On at least 125 occasions a US president has employed military forces without authorization from Congress. One of the most significant of these occasions was the

, where the United States led a peacekeeping

force to stop North Korea's invasion against South Korea. The conflict resulted in over 142,000 American casualties (about 40,000 deaths and over 100,000 injuries).

Russia

No formal declaration of war has been issued in the ongoing

Russo-Ukrainian War The Russo-Ukrainian War began in February 2014 and is ongoing. Following Ukraine's Revolution of Dignity, Russia Russian occupation of Crimea, occupied and Annexation of Crimea by the Russian Federation, annexed Crimea from Ukraine. It then ...

. When the Russian president,

Vladimir Putin Vladimir Vladimirovich Putin (born 7 October 1952) is a Russian politician and former intelligence officer who has served as President of Russia since 2012, having previously served from 2000 to 2008. Putin also served as Prime Minister of Ru ...

, launched the full-scale invasion of Ukraine in 2022, he used the euphemistic phrase '

special military operation "Special military operation" (also "special operation", and abbreviated as "SMO" or "SVO", or , ) is the official term used by the Russian government to describe the Russian invasion of Ukraine. It is widely considered a euphemism intended to ...

Other examples

The

Falklands War The Falklands War () was a ten-week undeclared war between Argentina and the United Kingdom in 1982 over two British Overseas Territories, British dependent territories in the South Atlantic: the Falkland Islands and Falkland Islands Dependenci ...

between

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

and the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

(April–June 1982) was never formally declared as a war.

References

Wars by type Warfare by type {{mil-stub

United States

Russia

Other examples

See also

References