Philosophers Works Dual monarchy occurs when two separate kingdoms are ruled by the same monarch, follow the same foreign policy, exist in a customs union with each other, and have a combined military but are otherwise self-governing.
After the 17th century brought three different civil wars, and a great deal of armed conflict, it was decided in 1707 to codify the unification of England and Scotland into the "perpetual" partnership promised by the Acts of Union.
Despite its historical success, the proposal to merge Ireland into Great Britain with some form of home rule was bandied about for decades before finally coming to naught in the Irish War of Independence.
Later historians have used the term to refer to other examples where one king ruled two states, such as Henry V and Henry VI, who were effectively kings of both England and France in the fifteenth century as a result of the formation of a puppet state in a large area of France during the Hundred Years' War,[2][3] Denmark–Norway, a dual monarchy that existed from 1537 to 1814,[4] a century of personal union of Sweden and Norway (1814–1905), and the Polish–Lithuanian Commonwealth (1569–1795).
In this sense Austria-Hungary was not a mere personal union, as both states shared a cabinet that governed foreign policy, the Army and common finances.