Modern diplomatic practice
Diplomatic agents
In 1961 the UN Conference on Diplomatic Intercourse and Immunities adopted the Vienna Convention on Diplomatic Relations to replace the 19th-century rules of Vienna and Aix. It specifies three classes of heads of mission: (1) ambassadors or nuncios accredited to heads of state and other heads of missions of equivalent rank, (2) envoys, ministers, and internuncios accredited to heads of state, and (3) chargés d’affaires accredited to ministers of foreign affairs. A chargé d’affaires ad interim is a deputy temporarily acting for an absent head of mission.
A fourth class established at Aix-la-Chapelle, that of minister-resident, lapsed in the 20th century, but some variations on the other classes were produced during that time. In 1918 Russia’s new regime abolished diplomatic ranks. When the Soviet government gained recognition, it accredited “plenipotentiary representatives,” known by the Russian abbreviation as “polpredy” and in English as “plenpots.” Because they lacked precedence under the rules then prevailing, however, the Soviet Union reverted to the previously used titles. The regime of Muammar al-Qaddafi in Libya sends Peoples’ Bureaus, which enjoy precedence under the present rules. Members of the Commonwealth accredit high commissioners to each other. Finally, the Vatican occasionally sends legates on special missions to Roman Catholic countries and in 1965 began to appoint pro-nuncios. It accredited apostolic nuncios only to those few Roman Catholic states where the papal envoy is always the doyen, or dean, of the diplomatic corps; internuncios elsewhere found themselves in the tiny remaining group of ministers. Hence, the title of pro-nuncio was devised to gain entry into the first class.
Emissaries of the first two classes are usually titled “extraordinary and plenipotentiary,” though they are neither; special full powers are issued to enable an envoy to sign a treaty. Precedence within each class is fixed by the date of presentation of credentials; otherwise, there is no real distinction between them. The senior ambassador by length of service is the doyen (unless the nuncio traditionally holds the post), who convenes and speaks for the local diplomatic corps as needed.