International alliance refers to the formal agreement of various states or political entities to cooperate in times of war or other crisis. Alliances may be primarily military in nature such as NATO or politically-oriented such as the European Union and have many purposes. They have been in existence for thousands of years beginning with tribal and clan agreements and then evolving into modern state-based alliances involving military and nonmilitary cooperation.
The study of alliances has been a central area of academic study both past and present. Some of the earliest work was done by the Indian military strategist Kautilya (c. 321–c. 297 bce) in his classic Artha-shastra (“The Science of Material Gain”). He argued that to have strategic value an alliance must be based on mutual benefit and not altruism or an ideological commitment.
An important part of his approach was the concept that a nation’s security depends on its ability to create a web of dependences on distant states by offering aid and support, so that if one ally is attacked it can mobilise others to come to its defence. This was an idea that was developed into what has been called a ‘deep alliance system’ which is capable of deterring threats by creating a collective capacity to counter them rather than just one or more allied states acting alone.
An example of this is the formation of the North Atlantic Treaty Organisation (NATO) in 1949. This was a collective security agreement that included all members except for the Soviet Union and Yugoslavia and allowed them to act together against any aggressor. More recently, the issue of the former Yugoslav Republic of Macedonia joining NATO was settled by a historic agreement allowing it to join as the 30th member of the Alliance under the name of the Republic of North Macedonia following its renaming in 2018.