THE EXTINCTION AND SUCCESSION OF STATES
125. Total Extinction. -- A State ceases to exist when it has lost the essential marks or distinguishing characteristics of a State.1 It may become extinct through voluntary action or as a result of conquest. Theoretically, extinction might result from natural causes, such as depopulation, extermination, total emigration, or a permanent condition of anarchy. But practically, States are extinguished through voluntary incorporation, forcible annexation, division into several States, or union with other States.2
Like the recognition of a new State or government, the recognition of a conquest, merger, division, or cession is the recognition of an accomplished fact, and should not be refused after resistance has virtually ceased, or when the old government has practically ceased to function. But a reasonable time should be permitted to elapse in order to enable the recognizing State to judge of the permanence and stability of the new condition of affairs, or to determine the capacity of the new State or States to carry out their international obligations. Such recognition is generally tacit.
States fully extinguished lose all international personality, and acquire the rights and obligations of the annexing or incorporating State. The observance of any agreements or promises made by the latter to such annexed or incorporated State is a matter of conscience, or of moral rather than of legal obligation.____________________
History abounds in examples of forcible annexations or cessions and conquests. Modern instances are the annexation of the South African (Transvaal) Republic and the Orange River Free State by Great Britain; and of the division of Poland in the 18th century.