- Act of state — United Nations (UN) — League of Nations — Collective security — Regional organizations
1 An alliance is a formal union or league between States designed to achieve a common objective through combined action. An alliance can be offensive or defensive in nature, though offensive military alliances are today considered contrary to international law. Alliances act to preserve and enhance the individual and collective power of States and to deter outsiders from aggressive or hostile acts. They may have economic, political, or security functions. These functions are defined in treaties setting out rules by which their members have agreed to be bound. Alliances are most frequently associated with defence and security collaboration (see also Self-Defence, Collective). Recognition of a common threat and shared security understandings lead alliance members into agreements on collective action and defensive measures. In the absence of war these may include joint military exercises, training of personnel, and the procurement of weapons. In the event of war, or the threat of war, a security alliance effectively binds members to mutual support and assistance through a variety of measures, whether diplomatic, economic, or military.
2 Alliances can be bilateral or multilateral. They may be permanent and institutionalized, as international organizations (International Organizations or Institutions, General Aspects) holding regular meetings and possessing formal organs and structures (eg North Atlantic Treaty Organization [NATO]), or limited and ad hoc without permanent structures (eg alignments, ententes, coalitions), established as short-term arrangements in response to a specific security threat and dismembered once that threat is overcome, or the purpose of the alliance ceases (eg the coalition of States that was assembled following Iraq’s invasion of Kuwait in 1990; Iraq-Kuwait War [1990–91]). The United Nations (UN), like its predecessor the League of Nations, incorporates the idea of a generalized multilateral security alliance. Geographically limited regional organizations, whose charters include a security dimension, may also act as security alliances, and can thus be understood as forming a sub-set of alliances.
3 Alliances often reflect the spheres of influence of dominant powers in the international system, as during the Cold War (1947–91). They have been closely related to the concept of a balance of power, long regarded as an important mechanism in regulating inter-State relations, though views differ as to whether or not they contribute positively or negatively to world peace. Other arrangements defined as alliances, whether for propaganda or other purposes, may share some of the above properties, but often lack the formal treaty component which binds members to concerted action. Hence the ‘Alliance for Progress’, an economic development programme for Latin America established by the US; or the ‘Third World Alliance’ signifying the loose union of developing countries around three causes: abstention from Cold War alliances; anti-colonialism (colonialism); and reform of the world economic system (Non-Aligned Movement [NAM]).
B. Historical Background
1. Alliances before 1919
4 Alliances have been concluded ever since sovereign communities have existed, to promote conquest, consolidate power, or resist aggression. Early alliances have been identified in ancient China and India, and among Greek and Italian city States. The Roman Empire used alliances to expand its territory. With the rise of the Western State system in the 15th century, alliance policy, in different contexts, became particularly significant. The Danubian monarchy, established in 1526 by an alliance of Austria, Bohemia, and Hungary, was later transformed into a union of two States: the Austrian Empire and the Kingdom of Hungary. The Triple Alliance (1688) and the Grand Alliance (1689) were both alliances of European powers directed against the power of France’s Louis XIV. Napoleon used a policy of alliances to extend his conquests. In turn, the Quadruple or Grand Alliance of 1814 between Great Britain, the Austrian Empire, Russia, and Prussia was designed to contain and overthrow the Napoleonic order. The defeat of Napoleon saw the renewal of the Quadruple Alliance in November 1815, heralding a new European order characterized as the Concert of Europe, a collective security system designed to prevent the return of Bonapartism and maintain a stable balance of power. France joined the Quadruple Alliance in 1818. The Holy Alliance (1815) (Holy Alliance between Austria, Prussia, and Russia [signed 11 (26) September 1815] [1815–16] 65 CTS 199), whose membership came to include most European monarchs, had similar aims and purposes.
5 The Convention of 8 July 1815 (Act Establishing the German Confederation [signed 8 June 1815] [1814–15] 2 BFSP 114) saw the foundation of the German Confederation designed to uphold the security and independence of its Member States against aggression, an arrangement which survived until 1866. In Latin America, the Paraguayan War of 1864–70 saw Paraguay defeated by a Triple Alliance of States comprising Argentina, Brazil, and Uruguay. The formation of the German Reich in 1871 was followed, in 1879, by the conclusion of a defensive alliance with Austria-Hungary against the threat of Russia. This double alliance, which became the Triple Alliance when Italy joined in 1882, was designed to preserve European peace against either French or Russian aggression. In turn, France and Russia concluded a defensive alliance in 1889—later joined by Britain, thus forming the Triple Entente—which was designed to achieve a balance of power, deter war, and to provide security to members should war break out. In World War I (1914–18) the members of these two alliances were named the ‘Central’ and ‘Allied’ powers respectively. Many States joined the Triple Entente, becoming ‘Allies’, though Russia exited the arrangement in 1917, concluding an armistice after the Bolshevik Revolution, then a separate peace with the Central Powers in 1918 (Brest-Litovsk, Peace of ). The United States of America, upon entering the war in 1917, declared itself an ‘Associate’ rather than an Allied Power, to retain freedom of action and signalling the lack of common agreement on the purposes and objects of the war.
2. Alliances 1919–45
6 Important changes and further attempts by States to regulate alliance behaviour followed World War I, though with mixed results. The perceived weaknesses of the alliance system prior to World War I, whether in preventing war or contributing to a stable balance of power encouraged the construction of a new international institution: the League of Nations, as provided for in the Peace Treaties after World War I. The League of Nations, established in 1920, incorporated the notion of a generalized security alliance designed to prevent the recurrence of conflict and regulate the behaviour of States. Indeed the League of Nations aspired to act as a collective security system by identifying and responding to any breaches of the peace. The League of Nations however proved largely ineffective either in preventing wars or the parallel creation of a competing alliance system which effectively undermined the principles of collective security. In the Rapallo Treaty (1922) (German-Russian Agreement [signed and entered into force 16 April 1922]  19 LNTS 247), the Locarno Treaties (1925) (Arbitration Conventions between Germany/Belgium, Germany/France [both signed 16 October 1925, entered into force 14 September 1926] 54 LNTS 305 and 317), and the Kellogg-Briand Pact (1928) (General Treaty for Renunciation of War as an Instrument of National Policy [signed 27 August 1928, entered into force 25 July 1929] 94 LNTS 57), different States sought alternative security arrangements outside the League of Nations framework. These efforts did not prevent the emergence of hostile alliances during the 1930s, notably the Agreement against the Communist International (Comintern) ([signed 25 November 1936, entered into force 25 November 1936]  140 BFSP 529), which, despite its purportedly defensive nature, revealed the expansionist aims of Germany and Japan, and Italy who joined in 1937. In World War II, as in World War I, two major alliances emerged for the purposes of conducting the war, named the ‘Allied’ and ‘Axis’ (or anti-Comintern) powers respectively. This ended with the defeat of the latter in 1945. The major Allied Powers in World War II comprised Great Britain, France (except during the German occupation 1940–44), the USSR (after June 1941), the US (after December 1941), and China. The Allied Powers included all the wartime members of the UN, signatories of the Declaration by United Nations (signed 1 January 1942, entered into force 1 January 1942] 204 LNTS 381).
3. Alliances since 1945
7 Alliances between 1945 and the end of the Cold War centred on the attempt to establish a more effective collective security framework in the UN and the creation of a parallel alliance system reflecting the division of the world into two opposing Cold War blocs. The United Nations Charter went further than the Covenant of the League of Nations, representing a more ambitious attempt at creating a generalized security alliance which outlawed the use or the threat of force except under prescribed conditions as stipulated by Art. 2 UN Charter (Use of Force, Prohibition of; Use of Force, Prohibition of Threat). The enforcement powers provided by the UN Charter were rarely used however. One exception was the Korean War (1950–53), in which the UN committed itself to collective action and enforcement measures designed to reverse North Korea’s attempt to reunify the two Koreas following their division after World War II. The action, though ultimately effective, was controversial because of the dominant role played by the US in the alliance of forces provided by Member States. Subsequently, the UN’s role as a major security provider was greatly reduced by the effects of the Cold War, though its members’ forces were increasingly used in post-conflict peacekeeping roles in both internal and international conflicts.
8 While the founders of the UN, like the League of Nations, had displayed a preference for universal over regional security arrangements, pressure from regional groups of States ensured that the final version of the UN Charter made ample provision for action by regional alliances and groups of States, while closely defining their remit and relationship with the UN (Regional Arrangements and the United Nations Charter). A number of permanent regional security alliances, together with other multipurpose regional institutions were established after 1945 including the League of Arab States (LAS) (1945), the Organization of American States (OAS) incorporating the Inter-American Treaty of Reciprocal Assistance of Rio de Janeiro (1947) ([signed 2 September 1947, entered into force 3 December 1948] 21 UNTS 93), the Western European Union (WEU) (1948), NATO, the Southeast Asia Treaty Organization (SEATO), the Central Treaty Organization (CENTO), and the ANZUS Pact (1951) (Australia, New Zealand and United States of America Security Treaty [signed 1 September 1951, entered into force 29 April 1952] 131 UNTS 83). These alliances and institutions were mainly promoted by Western powers, notably the US or Great Britain, to provide security and mutual defence, first in a post-colonial, then Cold War context. The response of the Soviet bloc to the Western-inspired alliance system was the consolidation of their own alliance in the Warsaw Treaty Organization or Warsaw Pact, as well as the attempt to construct a system of bilateral alliances with developing countries.
9 Other arrangements and unions established during the Cold War for the purposes of promoting regional security, though initially not all had alliance-like properties, included the European (Economic) Community, the Organization of African Unity (‘OAU’) in 1963 (African Union [AU]), the Association of Southeast Asian Nations (ASEAN) in 1967, the Cooperation Council for the Arab States of the Gulf (GCC) in 1981, and the Conference of Security and Cooperation in Europe in 1975 (Organization for Security and Cooperation in Europe [OSCE]). Of the above arrangements, the alliance roles played by NATO and the Warsaw Pact respectively, and the development of the EC as a security community stand out. Indeed the relative stability of the international system in the Cold War may be attributed less to the UN system and more to the existence of a stable balance of power characterized by the presence of two competing alliance systems representing the respective spheres of influence and supported by the military and nuclear power of the US and Soviet Union respectively. Further, the role of regional organizations in the Cold War cannot be regarded as broadly consistent with UN Charter purposes in respect of their alliance behaviour, notwithstanding their contribution to promoting order and stability.
10 The end of the Cold War had important consequences for alliances both inside and outside the UN framework. Firstly, superpower cooperation and the improved performance of the UN contributed to the solution of long-standing conflicts, leading some to point to the strengthening of the UN as a security alliance, and a corresponding weakening of traditional alliances and their roles. The Warsaw Pact was disbanded. However the persistence of NATO, of bilateral security arrangements—eg US–Israel or US–Japan—as well as the construction of new organizations like the Commonwealth of Independent States (CIS) and ad hoc alliances including the Western coalition in the 2003 Iraq–US War show that this is not the case (Iraq, Invasion of ). Secondly, both the UN itself and a growing number of regional institutions, acting independently and collectively, have become increasingly active in peace and security provision in post-Cold War conflict situations. Such involvement which covers peace enforcement, peacekeeping, and peacebuilding, represents an extension of alliance behaviour from preventing or combating inter-State aggression through mutual security and defence measures to addressing a range of security concerns, including those emanating from conflicts within States, often justified in the name of human rights and humanitarian assistance (Humanitarian Assistance in Cases of Emergency).
11 The Iraq–Kuwait War was unusual in involving, like the Korean War, a collective security enforcement operation supported by a coalition of forces drawn from UN Member States, whose purpose was to protect the territorial integrity and sovereignty of a fellow member, Kuwait. Other actions by the UN and regional organizations and groups of States have represented a newer understanding of collective security as suggested above, and hence a development of earlier peacekeeping roles. Regional institutions that have been active in this way include: in Europe, NATO, the OSCE, the CIS, the European Union; in Africa, the AU, the Economic Community of West African States (ECOWAS), the Southern African Development Community (SADC); in Pacific Asia, ASEAN and the ASEAN Regional Forum; and in the Americas, the Organization of American States.
C. Neutral States and Alliances
12 Until the first half of the 20th century, the concept of neutrality (Neutrality, Concept and General Rules), and the neutral State have enjoyed special status in alliances resulting from their status in international law, conferring on them and belligerent States (see also Belligerency) legal rights and obligations. A State is neutral if it has not declared support for any belligerent party in conflict. It follows therefore that a neutral State is impartial and cannot join any alliance or provide support to the members of an alliance, nor can it permit its territory to be used for war purposes by an alliance. Belligerent States or alliances of States for their part must respect the impartial status of neutrals, in respect, for example, of intercourse or trade with the enemy (Trading with the Enemy). However, if a neutral State is threatened by invasion it may call upon other States for aid and conclude alliances in order to defend its independence against aggression. Once the threat is removed the neutral State resumes its rights and obligations under its neutral status. The rights and status of neutral States were notoriously ignored by major alliances in the 20th century most notably in both World War I and World War II. Since 1945 the institution of neutrality has arguably lost much of its earlier relevance and hence fallen into decline. On the one hand, the UN Charter implies a commitment to neutrality except under conditions prescribed by the UN Security Council; on the other hand, the Cold War alliance system often rendered such impartiality impossible. Nonetheless Switzerland has retained its tradition of neutrality established in the 16th century; likewise the Constitutional Law on the Neutrality of Austria of 26 October 1955 declared the permanent neutrality of Austria.
13 States which gained their independence in the Cold War drew upon a modified form of the idea in the NAM, which was primarily a response to competition between the superpowers for the support of neutral States in the Cold War (Superpowers and Great Powers). Non-alignment embodies two criteria directly relevant to alliance behaviour: non-adherence to collective military pacts and non-participation in bilateral alliances with great powers.
D. Restrictions on Alliances in International Law
1. Treaties and Conventions
14 Alliances are typically established and internally regulated by treaties. Treaty provisions governing alliances are specific to members’ security concerns. Treaties define the casus foederis, or the particular circumstances under which a promise of mutual assistance may be implemented, as well as the type of assistance that may be supplied. When the casus foederis is established, alliance members agree coordinated action and/or military forces within a joint framework. In Art. 1 Holy Alliance between Austria, Prussia, and Russia, members pledged ‘to lend each other on all occasions and in all places aid and assistance’ in the event of aggression. In Art. 3 Inter-American Treaty of Reciprocal Assistance (1947), signatories agreed ‘that an armed attack by any State against an American State shall be considered as an attack against all the American States’. In the North Atlantic Treaty (April 1949), the US and 15 other States similarly committed themselves to support each other against any ‘armed attack’ in the North Atlantic area (Art. 5 North Atlantic Treaty). Under Art. 6 North Atlantic Treaty an ‘armed attack’ is defined as any attack on the territory, forces, vessels, or aircraft of any of the parties (see also Armed Forces; State Aircraft; State Ships). Some States may agree to be bound only by certain treaty provisions, as was the case of France in NATO. In withdrawing its Mediterra-nean fleet from NATO command and in developing an independent nuclear deterrent in the late 1950s, France acted outside the remit of Art. 3 North Atlantic Treaty, which commits the parties to ‘continuous and effective self-help and mutual aid…to maintain and develop their individual and collective capacity’.
15 Treaties of alliance are terminated on the same grounds as other treaties (Treaties, Termination). Any major or unforeseen change in the circumstances of an alliance can be invoked as grounds for exit, or a treaty may contain a clause regarding termination of membership by individual States, as is the case of Art. 13 North Atlantic Treaty. Prior to World War I, alliance treaties often included a ‘non-provocation’ clause relieving an ally of its obligations if any alliance partner provoked war.
16 Alliances are further regulated externally by those international conventions, treaties, and agreements to which their members are signatories; hence the laws governing them also comprise part of the larger body of international laws.
2. International Organizations
17 Since World War I, a significant source of regulation of alliances, notably in regard to the use of force, derives from the decisions of international organizations. Both the League of Nations and the UN, while aspiring to act as generalized security alliances in their own right, laid down rules regarding their own alliance behaviour in respect of the threat or use of force or coercive measures, while also regulating the behaviour of regional alliances and groups of States, and their relationship between regional and universal institutions.
(a) The League of Nations
to respect and preserve as against external aggression the territorial integrity and existing political independence of all Members. In the case of any such aggression or in the case of any threat or danger of such aggression, the Council shall advise upon the means by which this obligation shall be fulfilled.
19 The League Covenant displayed a preference for universal over regional or particularistic arrangements. Any treaty or alliance inconsistent with the terms of the League Covenant became invalid, and under Art. 19 League Covenant, Member States undertook to secure their release from any existing arrangements and not to enter into new ones. In Art. 21 League Covenant, the validity of regional understandings, consistent with League Covenant purposes, was noted with specific mention made of the Monroe Doctrine (Doctrines [Monroe, Hallstein, Brezhnev, Stimson]).
(b) The United Nations
20 The UN extended the restriction of the League of Nations as regards outlawing war as an instrument of policy, establishing rules regarding the use of force and appropriate measures to ensure peace and security. The main restriction is found in Art. 2 (4) UN Charter which states that ‘members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations’. In the event of any transgression, it is the role of the Security Council to determine the casus foederis: ‘The Council shall determine the existence of any threat to the peace, breach or the peace or act of aggression and shall make recommendations, or decide what measures shall be taken … to maintain or restore international peace and security’ (Art. 39 UN Charter). The operation of the UN as a security alliance is made explicit by Art. 4 (9) UN Charter, which obliges UN members to ‘join in affording mutual assistance in carrying out the measures decided upon by the Security Council’.
The parties to any dispute, the continuance of which is likely to endanger the maintenance of international peace and security, shall, first of all, seek a solution by negotiation, enquiry, mediation, conciliation, arbitration, judicial settlement, resort to regional agencies or arrangements, or other peaceful means of their own choice.
Nothing in the present Charter precludes the existence of regional arrangements or agencies for dealing with such matters related to the maintenance of international peace and security as are appropriate for regional action, provided that such arrangements or agencies and their activities are consistent with the Purposes and Principles of the United Nations.
E. Current Significance
23 The nature and relevance of alliances have shifted considerably since the Cold War era; however their continued existence looks secure. Despite a decline in defensive alliances, alongside the overall decline in international wars, the role of bilateral and multilateral, permanent and non-permanent alliances remain important in dealing with global security challenges. The UN has arguably become more active in its role as a generalized security alliance as the Iraq–Kuwait War (1990–91) and other subsequent interventions have shown; so have a range of regional institutions whether NATO or the OSCE, both in the European area and beyond, or the AU and the ECOWAS in Africa. There has been considerable growth in, and activity by, regional organizations with security provision while ad hoc alliance-making in response to specific threats continues as the US–Iraq War (Iraq, Invasion of ) demonstrates.
24 The relationship between the UN and regional organizations in matters relating to peace and security has received considerable attention since the end of the Cold War. In particular the idea of promoting a more effective partnership and division of labour between the UN and regional organizations has been endorsed by different UN Secretary-Generals, notably Boutros Boutros-Ghali in the Agenda for Peace (An Agenda for Peace: Preventive Diplomacy, Peacemaking and Peace-Keeping: Report of the Secretary-General Pursuant to the Statement Adopted by the Summit Meeting of the Security Council on 31 January 1992 [17 June 1992] UN Doc A/47/277–S/2411). Many such partnerships have been attempted across a wide variety of peacekeeping situations, for example in Africa—in Liberia and Sierra Leone—and Europe, particularly in the former Yugoslavia. The relationship between the UN and regional organizations in respect of security provision has often proved problematic in practice however, particularly with regard to the appropriate use of Chapter VIII of the UN Charter. This problem was exemplified by the bombings carried out by NATO against the Federal Republic of Yugoslavia in 1999, when the NATO-led coalition took enforcement action without prior UN authorization. It is controversial whether the US-led alliance in the US–Iraq war (2003) took action without UN authorization.
25 The future direction of alliances and the relationship between different types of alliances and the UN remain uncertain and will depend, as before, on many factors, including the global balance of power. However, the further creation and development of alliances, whether ad hoc or permanent, and their continuing expansion to deal with new security challenges such as terrorism, weapons of mass destruction, and transnational organized crime looks set to continue. If alliances, in some senses, have lost their earlier utility they have acquired new and equally significant security roles. Continuing critiques of alliance behaviour notwithstanding, they may be regarded as playing generally positive roles in maintaining international peace and security.
- SM Walt The Origins of Alliances (Cornell University Press Ithaca 1987).
- TJ Farer ‘The Role of Regional Collective Security Arrangements’ in TG Weiss (ed) Collective Security in a Changing World (Lynne Rienner Boulder 1993) 153–86.
- A Roberts and B Kingsbury (eds) United Nations, Divided World: The UN’s Role in International Relations (2nd ed Clarendon Oxford 1993).
- C Schreuer ‘Regionalism v Universalism’ (1995) 6 EJIL 477–99.
- GH Snyder Alliance Politics (Cornell University Press Ithaca 1997).
- M Pugh and WPS Sidhu (eds) The United Nations and Regional Security: Europe and Beyond (Lynne Rienner Boulder 2003).
- BL Job ‘The UN, Regional Organizations, and Regional Conflict: Is there a Viable Role for the UN?’ in RM Price and MW Zacher (eds) The United Nations and Global Security (Palgrave Macmillan New York 2004) 227–43.
- S Kaplan NATO Divided, NATO United: The Evolution of an Alliance (Praeger Westport 2004).
- D Sarooshi ‘The Security Council’s Authorisation of Regional Bodies to Use Force’ in V Lowe and others (eds) The United Nations Security Council and War: The Evolution of Thought and Practice since 1945 (OUP Oxford 2008) 226–47.
- Charter of the United Nations (adopted 26 June 1945, entered into force 24 October 1945) 145 BSP 805.
- Covenant of the League of Nations (signed 28 June 1919, entered into force 10 January 1920) (1919) 225 CTS 195.
- North Atlantic Treaty (signed 4 April 1949, entered into force 24 August 1949) 34 UNTS 243.
- Treaty of Friendship, cooperation and Mutual Assistance (signed 14 May 1955, entered into force 6 June 1955) 219 UNTS 3 (Warsaw Pact).