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|Basic forms of government|
Diarchy (or dyarchy; from the Greek δι- / δύο meaning "two" and ἄρχω meaning "I rule") is a form of government in which two individuals ("diarchs") are joint heads of state. Most diarchs hold their position for life, passing the position to their children or other family members.
Diarchy is one of the oldest forms of government: examples include ancient Sparta, Rome, Carthage as well Germanic and Dacian tribes. Several ancient Polynesian societies also exhibited a diarchic political structure. Ranks in the Inca Empire were structured in moieties, with two occupants of each rank, but with different prestige, one hanan (upper) and one hurin (lower). In modern usage, diarchy means a system of dual rule, whether this be of a government or of an organization. Such 'diarchies' are not hereditary.
Modern examples of diarchies are the Principality of Andorra, whose heads of state are the President of France and the Bishop of Urgell; the Republic of San Marino, led by two collegial Captains Regent; and the Kingdom of Swaziland, where the joint heads of state are the King and his mother.
The Principality of Andorra is a parliamentary co-principality with the President of France and the Bishop of Urgell (Catalonia, Spain) as co-princes. This peculiarity makes the President of France, in his capacity as Prince of Andorra, an elected reigning monarch, even though he is not elected by a popular vote of the Andorran people, but rather by the French people.
The Captains Regent (Italian: Capitani Reggenti) of the Republic of San Marino are elected every six months by the Grand and General Council — the country's parliament. The duo serve as heads of state and government. Normally the Regents are chosen from opposing parties. They serve a six-month term.
The Kingdom of Swaziland is a diarchy in which the King (Ngwenyama) rules in conjunction with his mother, the Queen Mother (Ndlovukati). In practice, however, most power is vested in the King, though it is often argued that the giving of authority wholesale to the royal male in this way is a neo-traditionalistic as opposed to truly traditional custom.
The Gonghe Regency (meaning joint harmony) of the Zhou dynasty was ruled jointly by two dukes for a short period according to Han Dynasty historian Sima Qian, but it is more likely that the Count of Gong was the actual single ruler (according to bronze tapestries).
Russia February - October 1917
The Independent State of Samoa was established as a diarchy in 1962, with two of the nation's four paramount chiefs; Malietoa Tanumafili II and Tupua Tamasese Mea'ole declared joint heads of state, or O le Ao o le Malo for life. Samoa has consistently had a single head of state since Mea'ole's death in 1963. In 2007 it transitioned to an elected head of state following Tanumafili's death.
- Erik and Alrik
- Yngvi and Alf
- Björn at Hauge and Anund Uppsale
- Eric the Victorious and Olof Björnsson
- Eric the Victorious and Olof Skötkonung
- Halsten Stenkilsson and Inge I
- Philip and Inge II
In England, Scotland, and Ireland
- William III and Mary II held joint sovereignty over the three kingdoms of England, Scotland, and Ireland from 1688 to 1694.
- Mary I and Philip ruled together over England, Ireland, and the Habsburg dominions from 1554 to 1558 through Queen Mary's Marriage Act making Phillip King of England by jure uxoris.
The Lithuanian Grand Dukes typically selected submonarchs from their families or loyal subjects to assist controlling the Grand Duchy. However, the Grand Dukes remained superior.
- Vytenis (superior) and Gediminas
- Gediminas (superior) and an unknown duke of Trakai, presumably Gediminas's son.
- Algirdas (superior) and Kęstutis
- Jogaila (superior) and Kęstutis
A slightly different system developed for a brief period after Vytautas became Grand Duke, where nominally Vytautas ruled together with Jogaila, who took the title of aukščiausiasis kunigaikštis (Supreme Duke), but he has not once used the title to take any action, and in general the powers invested in the title were not clearly stated in any documents, besides the Pact of Horodlo, which guaranteed that Jogaila would have to approve the selection of a Lithuanian Grand Duke. The title was not used by any other king of Poland after Jogaila.
- Vytautas (Grand Duke) and Jogaila (Supreme Duke)
- Švitrigaila (Grand Duke) and Jogaila (Supreme Duke) for a brief period, until Švitrigaila declared war on Poland
- Sigismund I of Lithuania (Grand Duke) and Jogaila (Supreme Duke) until Jogaila's death.
Classical Sparta in ancient Greece was ruled for over 700 years by two kings at a time (q.v., List of Kings of Sparta), belonging to two separate dynasties, who could veto one another's actions. In addition Sparta had groups of officials known as Ephors and a council of elders.
Spiritual and temporal kings
Another common pattern of diarchy has one king in charge of spiritual matters and another, usually subordinate to the first, in charge of temporal or military matters. This pattern was followed in early Hungarian society by the spiritual kende and the military gyula. The Khazars were ruled by the spiritual khagan and the military bek. During the shogunate of Japan, the emperor held spiritual and nominal authority over the whole country, while the shogun held temporal authority.
In precolonial Igboland, southeastern West Africa, some clans and city-states were governed by a chief chosen by and from a Council of Elders ("Ndi Ichie" or "Ndi Nze na Ozo") as well as a Chief Priest. While the appointed chief took care of the temporal affairs, the Chief Priest was in charge of the spiritual well-being of the community and served as an oracle or the "mouthpiece of the gods."
Australian Defence Organisation
The Australian Defence Organisation (ADO) is an Australian Government organisation which consists of the Australian Defence Force (ADF) and the civilian Department of Defence personnel supporting the ADF. The Chief of the Defence Force and the Secretary of the Department of Defence jointly manage the ADO under a "diarchy" wherein both report directly to the Minister for Defence. The ADO diarchy is a governance structure unique in the Australian Commonwealth public service.
On 20 August 1917 in the British House of Commons, the newly appointed Secretary of State, Edwin Samuel Montagu, made the "Grand Declaration", which said that British policy was "increasing association of Indians in every branch of the administration and the gradual development of self-governing institutions with a view to progressive realization of responsible government in British India as an integral part of the British Empire".
In pursuance of the policy laid down in the announcements by Montagu, the Secretary of State and Frederic Thesiger, 1st Viscount Chelmsford, the Governor-General of India, made an extensive tour of India in 1917 and 1918 and produced the Montague - Chelmsford Report containing recommendations that paved the way for Government of India Act 1919.
That act of 1919 introduced diarchy, or dual government, in the provinces, where the executive was to be headed by a governor appointed by the Secretary of State, who could consult the Governor General. The governor was responsible to the Secretary of State for acts of omission and commission. He was to maintain law and order in the province and ensure that the provincial administration worked smoothly. In respect of transferred subjects, he was to be assisted by his ministers whereas reserved subjects were to be administered by the Governor General and his executive council.
The members of the Executive council were to be appointed by Secretary of State and were responsible to him in all matters. There were certain matters that he was to administer at his own discretion, in which he was responsible to the Secretary of State. Each councillor was to remain in office for a period of four years. Their salaries and service conditions were not subject to the vote of provincial legislature. All decisions in the council were to be taken by a majority of votes, the Governor being able to break ties.
The First Minister and deputy First Minister of Northern Ireland serve as the joint heads of the country's Executive. Under the terms of the 1998 Good Friday Agreement, both positions have identical public power within the Northern Ireland Assembly, a devolved government of the United Kingdom.