A preemptive war is a war that is commenced in an attempt to repel or defeat a perceived imminent offensive or invasion, or to gain a strategic advantage in an impending (allegedly unavoidable) war shortly before that attack materializes. It is a war that 'breaks the peace' before an impending attack occurs.
Preemptive war is sometimes confused with preventive war: the difference is that a preventive war is launched to destroy the potential threat of the targeted party, when an attack by that party is not imminent or known to be planned. The U.S. Department of Defense defines a preventive war as an armed conflict "initiated in the belief that military conflict, while not imminent, is inevitable, and that to delay would involve greater risk." A preemptive war is launched in anticipation of immediate aggression by another party. Most contemporary scholarship equates preventive war with aggression, and therefore argues that it is illegitimate.Shue, Henry and Rhodin, David (2007). Preemption: Military Action and Moral Justification. Oxford University Press. p. 116. The waging of a preemptive war has less stigma attached than does the waging of a preventive war.Shue and Rodin 2007, p. 118.
Article 2 (4) of the UN Charter requires that states refrain from the initiation of armed conflict, that is being the first to 'break the peace' unless authorized by the UN Security Council as an enforcement action under Article 42. The UN Charter reads in Article 51 that: "Nothing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a member of the United Nations." Some scholars believe that the effect of Article 51 is only to preserve this right when an armed attack occurs. Most scholars view the "inherent right of collective or individual self-defense" in Article 51 as including preemptive, or anticipatory, self-defense, as recognized under customary international law and articulated in the Caroline test. A US Army sponsored discussion of various justifications for preemptive, preventive and 'precautionary' war.
Theory and practice Prior to World War I
As early as 1625, Dutch jurist Hugo Grotius characterized a state's right of self-defense to include the right to forestall an attack forcibly. In 1685, the Scottish government conducted a preemptive military strike against Clan Campbell. In December 1837, a legal precedent regarding preemptive wars was established in the Caroline affair, which occurred during the Upper Canada Rebellion. A group of Reformist rebels had established themselves on Navy Island, and American sympathizers had been supplying them with volunteers and military equipment via the steamboat Caroline. On the night of December 29, a force of Canadian militiamen and law enforcement officials went across the Canada–United States border and drove off Carolines crew before setting the ship on fire and sending it over Niagara Falls. Following the ship's destruction, British ambassador to the United States Henry Stephen Fox argued that the attack was an act of self-defence. In a letter to Fox, United States Secretary of State Daniel Webster argued that a self-defence claimant would have to show that the:
Webster further wrote that when a nation uses force "within the territory of a power at peace, nothing less than a clear and absolute necessity can afford ground of justification"."The Diplomatic and Official Papers of Daniel Webster While Secretary of State" pp. 105, 110 (Harper & Bros. 1848). That formulation is part of the Caroline test, which "is broadly cited as enshrining the appropriate customary law standard."Duffy, Helen (2005). The 'War on Terror' and the Framework of International Law. Cambridge University Press. p. 157.
World War I (1914–1918)
The Austro-Hungarian Chief of the General Staff, Franz Conrad von Hötzendorf, argued for a preemptive war against Serbia in 1913. There is however no agreement among historians that Conrad's proposals were preemptive and not preventive. According to other historians, Conrad (a social Darwinist) had proposed a preventive war against Serbia more than 20 times before, starting in 1909.Preemption: Military Action and Moral Justification, OUP 2007, p. 31 Serbia had the image of an aggressive and expansionist power and was seen as a threat to Austria-Hungary in Bosnia and Herzegovina. The assassination of Archduke Franz Ferdinand (June 1914) was used as an excuse for Austria-Hungary to attack Serbia, leading to World War I.
During the course of the destructive and costly World War I, for the first time in history, the concept of "the war to end war" began to be seriously considered. Discussion of Woodrow Wilson's desire to make World War I the War to End All Wars. As a further expression of that hope, upon the conclusion of the war, the League of Nations was formed. Its primary aim was to prevent war, as all signatories to the League of Nations Covenant were required to agree to desist from the initiation of all wars, preemptive or otherwise. All of the victorious nations emerging out of World War I eventually signed the agreement, with the notable exception of the United States. Article summarizing the primary objective of the League of Nations.
League of Nations period (1919–1939)
In the 1920s, the League peaceably settled numerous international disputes and was generally perceived as succeeding in its primary purpose. It was only in the 1930s that its effectiveness in preventing wars began to come into question. Such questions began to arise when it first became apparent in 1931 that it was incapable of halting aggression by Imperial Japan in Manchuria. In the Mukden Incident, Japan claimed to be fighting a "defensive war" in Manchuria, attempting to "preempt" supposedly-aggressive Chinese intentions towards the Japanese. According to the Japanese, the Republic of China had started the war by blowing up a South Manchurian Railway line near Mukden and that since the Chinese were the aggressors, the Japanese were merely "defending themselves."' A predominance of evidence has since indicated that the railway had actually been blown up by Japanese operatives. Details of the Mukden Incident
In 1933, the impotency of the League became more pronounced when notices were provided by Japan and Nazi Germany that they would be terminating their memberships in the League. Fascist Italy shortly followed suit by exiting the League in 1937. A timeline of all major League events. Soon, Italy and Germany also began engaging in militaristic campaigns designed to either enlarge their borders or to expand their sphere of military control, and the League was shown to be powerless to stop them. The perceived impotency of the League was a contributing factor to the full outbreak of World War II in 1939. Description of the demise of the League of Nations. The start of World War II is generally dated from the event of Germany's invasion of Poland. It is noteworthy that Germany claimed at the time that its invasion of Poland was in fact a "defensive war," as it had allegedly been invaded by a group of Polish saboteurs, signaling a potentially-larger invasion of Germany by Poland that was soon to be under way. Thus, Germany was left with no option but to preemptive invade Poland to halt the alleged Polish plans to invade Germany. It was later discovered that Germany had fabricated the evidence for the alleged Polish saboteurs as a part of the Gleiwitz incident.
World War II (1939–1945)
Once again, during the course of the even more widespread and lethal World War II, the hope of somehow definitively ending all war, including preemptive war, was seriously discussed. That dialogue ultimately resulted in the establishment of the successor organization to the League, the United Nations (UN). As with the League, the primary aim and hope of the UN was to prevent all wars, including preemptive wars. Unlike the League, the UN had the United States as a member.
In analyzing the many components of World War II, which one might consider as separate individual wars, the various attacks on previously-neutral countries, and the attacks against Iran and Norway might be considered to have been preemptive wars.
As for the 1940 German invasion of Norway, during the 1946 Nuremberg trials, the German defense argued that Germany had been "compelled to attack Norway by the need to forestall an Allied invasion and that her action was therefore preemptive."Myres Smith McDougal, Florentino P. Feliciano, The International Law of War: Transnational Coercion and World Public Order pp. 211, 212 The German defence referred to Plan R 4 and its predecessors. Norway was vital to Germany as a transport route for iron ore from Sweden, a supply that Britain was determined to stop. One adopted British plan was to go through Norway and occupy cities in Sweden."COMMAND DECISIONS", CENTER OF MILITARY HISTORY DEPARTMENT OF THE ARMY WASHINGTON, D.C., 2000. URL p. 59 "The British plan which was adopted was more modest. While ostensibly intended to bring Allied troops to the Finnish front, it laid its main emphasis on operations in northern Norway and Sweden. The main striking force was to land at Narvik and advance along the railroad to its eastern terminus at Lulea, occupying Kiruna and Gallivare along the way. By late April two Allied brigades were to be established along that line.""COMMAND DECISIONS", CENTER OF MILITARY HISTORY DEPARTMENT OF THE ARMY WASHINGTON, D.C., 2000. URL p. 66, 67 "The British held back two divisions from France, intending to put them into the field in Norway, and planned to expand their force eventually to 100,000 men. The French intended to commit about 50,000. The British and French staffs agreed that the latter half of March would be the best time for going into Norway;" An Allied invasion was ordered on March 12, and the Germans intercepted radio traffic setting March 14 as deadline for the preparation."COMMAND DECISIONS", CENTER OF MILITARY HISTORY DEPARTMENT OF THE ARMY WASHINGTON, D.C., 2000. URL p.67,68 "The objectives were to take Narvik, the railroad, and the Swedish ore fields;" "an intercepted radio message setting 14 March as the deadline for preparation of transport groups indicated that the Allied operation was getting under way. But another message, intercepted on the 15th, ordering the submarines to disperse revealed that the peace [in Finland] had disrupted the Allied plan." Peace in Finland interrupted the Allied plans, but Hitler became rightly convinced that the Allies would try again and ordered Operation Weserübung.
The new Allied plans were Wilfred and Plan R 4 to provoke a German reaction by laying mines in Norwegian waters, and once Germany showed signs of taking action, Allied forces would occupy Narvik, Trondheim and Bergen and launch a raid on Stavanger to destroy Sola airfield. However, "the mines were not laid until the morning of 8 April, by which time the German ships were advancing up the Norwegian coast.""COMMAND DECISIONS", CENTER OF MILITARY HISTORY DEPARTMENT OF THE ARMY WASHINGTON, D.C., 2000. URL p. 68 However, the Nuremberg trials determined that no Allied invasion was imminent and therefore rejected Germany's argument of being entitled to attack Norway.
In August 1941, Soviet and British forces jointly invaded Iran with the aim of preempting an Axis coup.
Six Day War (1967)