A personal union occurs when two otherwise independent states (each with their own territories, governments, etc.) come to share the same monarch. Has it ever come to pass that two member states of a personal union fought a war with each other? Note that I mean to exclude civil wars and rebellions; I am interested in those cases where the legitimate, recognized government of a country prosecutes a war against the legitimate, recognized government of another country, and both governments recognize the same monarch as head of state.

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    Who decides what the "legitimate, recognized government of a country" is? Apr 27, 2016 at 13:56
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    Yeah, I'd say the "legitimacy" angle should probably not be played up so much in this question. Ultimately legitimacy was often decided on the battlefield.
    – T.E.D.
    Apr 27, 2016 at 14:23
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    Charles Stuart, England and Scotland?
    – Ne Mo
    Apr 27, 2016 at 17:38
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    Adding to @NeMo's comment - the Bishops' War en.wikipedia.org/wiki/Bishops%27_Wars Scotland's Laws do differ from English even now and they had a separate Parliament up to 1707
    – mmmmmm
    Apr 28, 2016 at 10:20
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    @IanRingrose: For the purposes of my question, I think the only deciders who matter are the belligerents themselves. If both of them recognize each other's legitimacy as independent governments, then that's fine with me.
    – Psychonaut
    Apr 28, 2016 at 10:39

4 Answers 4


King George VI was at war with himself when the Dominions of Pakistan and India, recently declared independent of Britain, fought each other. Correct me if I am wrong here.


The Bishops war between the Covenanters and the Episcopals, in 17th century Scotland. I stand to be corrected, but I don't think the Covenanters had a candidate to replace Charles. So we can say that they accepted he was head of state. The English were against the Covenanters (although it was more complicated than that).

England and Scotland had separate parliaments. I'm not sure that we can speak of separate state and government at this time, though.

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    That is pretty much the definition of a personal union.
    – MCW
    May 1, 2016 at 12:22
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    Doesn't the question specifically exclude civil wars and rebellions (which this is)? May 1, 2016 at 15:03
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    I think it would be hard to say whether it was a civil war or a war between England and Scotland. If the latter, the two were legally separate countries until 1707.
    – Ne Mo
    May 1, 2016 at 15:42
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    It was an attempt by the Covenanters to overthrow their head of state (i.e. King Charles). Charles used forces loyal to him from both Scotland and England to defend his position. This was not the English state vs the Scottish state. Therefore does not answer the question. And the same can be said for the later intervention of Scottish forces in the English civil wars.
    – Steve Bird
    May 1, 2016 at 16:44
  • Did the Covenanters want to establish a separate Scottish republic, or what? That's not a rhetorical question or an argument, I'm asking because I don't know. If they didn't want Charles they must surely have wanted a different king, or else a republic.
    – Ne Mo
    May 1, 2016 at 17:15

The best and closest examples are likely to be civil wars in realms that consisted of two or more kingdoms in personal union. Thus it may be a matter of interpretation how well they satisfy your question.

During the 30 years war Emperor Ferdinand II was king of (part of) Hungary,etc., and Bohemia, Archduke of Austria, etc. At one point Hungarian Rebel leaders and their troops were in the Hofburg threatening Ferdinand to get him to sign a document giving them power when a regiment of his soldiers entered the Hofburg and turned the tables. This is close to being a war between the kingdoms of Hungary and Bohemia (and the Austrian lands) in a personal union. In 1683 Hungarian rebel forces were cooperating with the Turks besieging Vienna and were defeated separately. This again is close to being a war between the kingdoms of Hungary and Bohemia (and the Austrian lands) in personal union.

There may have been Polish-Lithuanian wars when they were in personal union and there may have been Swedish-Polish wars when they were in personal union. There may have been Swedish-Danish wars when they were in personal union in the Union of Kalmar.

Thus it may be a matter of interpretation how well they satisfy your question.

  • There were certainly wars between Sweden and Denmark during the Union of Kalmar, but AFAIK none that would fit the criteria. The closest you would come was for a period when Sweden had an elected Regent, who was recognised by the Danish king, but said king was not also elected King of Sweden (even if the union was not officially dissolved). The war to evict Sigismund also falls under "rebellion".
    – andejons
    May 2, 2016 at 6:56

Depending of how you state the events, a candidate could the War of Spanish Succession.

Philip V of Spain was recognized by the Crown of Aragon as King, but he was deeply distrusted (in part of being French, in part because the Borbon dinasty had imposed centralism in France) and later the Crown of Aragon came to support Charles II.

Of course, depending of how you state it, it can be also considered a civil war or just an insurrection again their ruler, but I doubt you will find many examples so close to what you ask for.

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