Succession of states is a theory and practice in international relations regarding successor states. A successor state is a sovereign state over a territory and populace that was previously under the sovereignty of another state. The theory has its root in 19th-century diplomacy. A successor state often acquires a new international legal personality, which is distinct from a continuing state, also known as a continuator, which despite change to its borders retains the same legal personality and possess all its existing rights and obligations (such as a rump state).
A state succession can be characterized as either being universal or partial. A universal state succession occurs when one state is completely extinguished and its sovereignty is replaced by that of one or more successor states. A partial state succession occurs when the state continues to exist after it has lost control of a part of its territory.
An example of a partial state succession is the case of the split of Bangladesh from Pakistan, there was no challenge to Pakistan's claim to continue to exist and to retain its membership of the United Nations: it was a continuator and not a successor. Bangladesh eventually was recognized as a new state: it was a successor and had to apply for UN membership.
Consequent upon the acquisition of international legal personality, the difficult matter of succession to treaty rights and obligations arises. Succession may refer to the transfer of rights, obligations, or property from a previously well-established predecessor state to its successor state, and can include overseas assets such as diplomatic missions, foreign-exchange reserves, and museum artifacts; and participation in treaties in force at the date of succession or international organizations. In an attempt to codify the rules of succession of states, the 1978 Vienna Convention entered into force on November 6, 1996.
In their application to the acquisition of independence, distinctions should be drawn between different cases though the line of demarcation is not always clear:
There are several recent examples where a succession of states, as described above, has not been entirely adhered to. This is mostly a list of the exceptions that have occurred since the creation of the United Nations in 1945. In previous historical periods, the exceptions would be too many to list.
The Taliban state in Afghanistan (the Islamic Emirate of Afghanistan) became the de facto government of nearly all the country in the mid-1990s, but the Afghan Northern Alliance was still recognised by many nations and retained the UN seat.
The People's Republic of China (PRC) was established in 1949 in Mainland China, claiming "succession" from the Republic of China (ROC). However, the succession of the PRC as the state of "China" was not initially recognized by many states because of Cold War politics and because the ROC continued to exist on the island of Taiwan and other islands, such as Penghu, Kinmen, Matsu, Pratas and Taiping. Despite this situation, the ROC in Taiwan maintained their membership as "China" in the United Nations, and a permanent seat on the UN Security Council. However, the PRC was granted the seat of "China" in the United Nations and Security Council in 1971, in place of the ROC whose recognition was withdrawn and the representatives it had sent were expelled as unlawful representatives of China. This was done through the adoption of General Assembly Resolution 2758. As of 2014 , the PRC exercises sovereignty over mainland China, while the ROC continues to be unrecognized by the United Nations but exercises sovereignty over the Taiwan Area, with both claiming they are the sole legitimate government of both the mainland and Taiwan. The ROC also claims borderlands unclaimed by the PRC, most notably (Outer) Mongolia.
Ireland, then called the Irish Free State, seceded from the United Kingdom in 1922. The new state took the view that when a new state comes into being after formerly being part of an older state, its acceptance of treaty relationships established by the older state is a matter for the new state to determine by express declaration, or by conduct in the case of each individual treaty. In practice, however, the Irish regarded the commercial and administrative treaties of the United Kingdom previously applying to the territory of the Irish Free State as remaining in force.
Israel took the view that, by virtue of its declaration of independence in 1948, a new international personality was created and that it started with a clean slate and was bound only by such of the former international obligations affecting the territory as Israel might accept.
When Democratic Kampuchea led by Pol Pot was militarily displaced by the Vietnamese-backed People's Republic of Kampuchea, the country's United Nations seat was held by Democratic Kampuchea for many years. It is now held by the Kingdom of Cambodia.
An important tenet of the modern state of Republic of Korea is that the Korean Empire's incorporation into the Empire of Japan from 1910 to 1945 constituted an illegal occupation. In 1919 when the Provisional Government of the Republic of Korea was formed it claimed continuity directly from their pre-1910 status. In 1948 when the modern Republic of Korea was formed it claimed that it was identical with Provisional Government of the Republic of Korea and that the Provisional Government succeeded the Korean Empire.
There is some debate over whether the modern Republic of Turkey is a continuing state to the Ottoman Empire or a successor. The two entities fought on opposing sides in the Turkish War of Independence (1919-23), and even briefly co-existed as separate administrative units (whilst at war with one another): Turkey with its capital in Angora (now Ankara) and the Ottoman Empire from Constantinople (now Istanbul), but this type of scenario is also common in civil wars. The nationalist faction, led by Mustafa Kemal who defected from the Ottoman army, established the modern republic as a nation-state (or new government regime) by defeating the opposing elements in the independence war. There remains debate about whether the Turkish War of Independence was a war of independence, or a civil war that led to a regime change.
When Pakistan became independent it claimed that it was automatically a member of the United Nations, as British India had been a founding member of the United Nations despite its colonial status. The United Nations Secretariat however expressed the following opinion:
From the viewpoint of International Law, the situation is one in which part of an existing State breaks off and becomes a new State. On this analysis there is no change in the international status of India; it continues as a State with all treaty rights and obligations, and consequently with all rights and obligations of membership in the United Nations. The territory which breaks off--Pakistan--will be a new State. It will not have the treaty rights and obligations of the old State and will not, of course, have membership in the United Nations. In International Law, the situation is analogous to the separation of the Irish Free State from Britain, and Belgium from the Netherlands. In these cases the portion which separated was considered a new State, and the remaining portion continued as an existing State with all the rights and duties which it had before.
International convention since the end of the Cold War has come to distinguish two distinct circumstances where such privileges are sought by such a successor state, in only the first of which may such successor states assume the name or privileged international position of their predecessor. The first set of circumstances arose at the dissolution of the Union of Soviet Socialist Republics (USSR) in 1991. One of this federation's constituent republics, the Russian Federation has declared itself to be "the continuator state of the USSR" on the grounds that it contained 51% of the population of the USSR and 77% of its territory. In consequence, Russia agreed that it would acquire the USSR's seat as a permanent member of the United Nations Security Council. This was also accepted by the rest of the former states of the USSR; in a letter dated 24 December 1991, Boris Yeltsin, at the time President of the Russian Federation, informed the Secretary-General that the membership of the Soviet Union in the Security Council and all other United Nations organs was being continued by the Russian Federation with the support of the 11 member countries of the Commonwealth of Independent States. All Soviet embassies became Russian embassies.
On the other hand, the Baltic states represent a special case. An important tenet of the modern states of Estonia, Latvia and Lithuania is that their incorporation into the Soviet Union from 1940 to 1991 constituted an illegal occupation. In 1991 when each Baltic state regained their independence they claimed continuity directly from their pre-1940 status. Many other states share this view, and as such, these states were not considered either predecessor or successor states of the Soviet Union. As a consequence, the Baltic states were able to simply re-establish diplomatic relations with countries, re-affirm pre-1940 treaties still in force, and resume membership to international organizations.
After four of the six constituent republics of the Socialist Federal Republic of Yugoslavia seceded in 1991 and 1992, the rump state, renamed the Federal Republic of Yugoslavia, stated it was the continuation of the state of Yugoslavia--against the objections of the newly independent republics. Representatives from Belgrade continued to hold the original Yugoslavian UN seat--however, the United States refused to recognize it. The remaining territory of the federation was less than half of the population and territory of the former federation. In 1992 the Security Council on September 19 (Resolution 777) and the General Assembly on September 22, decided to refuse to allow the new federation to sit in the General Assembly under the name of "Yugoslavia" on the theory that the Socialist Federal Republic of Yugoslavia had dissolved. The Federal Republic of Yugoslavia (later renamed Serbia and Montenegro) was admitted as a new member to the United Nations in 2000; in 2006, Montenegro declared independence and Serbia continued to hold the federation's seat. Additionally, Kosovo declared independence in 2008.