Recently, I started to read about history as a hobby like I used to when I was a kid. I realized that reading about "generic history" does not do it for me anymore. Instead I have some particular interests that I would like to follow up on, but I do not know where to begging.

Are there examples of two or more medieval kingdoms trying to unify/merge? Yet, they failed to do so because of internal strife, internal resistance, or cultural/religious differences?

From what I remember, I know that kingdoms merging because of marriage or free association was rare. I also remember that there was something about Queen Mary I of England marrying the heir apparent to the crown of Spain, Philip, in 1554, but that is about it.

Any interesting examples, that I could read about (with literature recomendatiosn if poossible)?

  • What do you mean by "kingdoms"? Many sovereign states existed as principalities, grand duchies, duchies, etc., across the entire breadth of the (dissolved) Carolingian Empire. (In this context, one might interpret "sovereign" as meaning the family members could marry "royalty" without rules on morganatic issue being triggered.) Commented Oct 9, 2022 at 2:35
  • @Pieter Geerkens Your comment has the worse definition of "sovereign" I have ever seen.
    – MAGolding
    Commented Oct 9, 2022 at 4:39
  • 1
    @MAGolding: Then proposing a better one should be trivial. I'm open to suggestions in that regard. Commented Oct 9, 2022 at 11:48
  • @Pieter Geerkens. Try looking up dictionary definitions of"sovereign" to see whether it mentions anything about marriages between rulers. There are many cases where sovereign rulers married women belonging the families of their own vassals who were clearly not sovereign.
    – MAGolding
    Commented Oct 10, 2022 at 17:14
  • I take it that you aren't including two countries trying to conquer each other and failing?
    – Mark Olson
    Commented Oct 11, 2022 at 0:30

2 Answers 2


The Rough Wooing (Wikipedia) might be an example of what you are looking for. Mary had inherited the Scottish Throne as she was just 6 days old. While she was still a toddler, the plan was hatched to marry her to the English crown prince Edward (about 5 years older than Mary) and thereby unify England and Scotland. This was the Treaty of Greenwich (Wikipedia).

The Scottish Parliament ultimately decided against it, and did not ratify the treaty. The English tried to make them. It got ugly, very ugly. It didn't work.

  • 2
    By what time scale do you count this as "medieval"? Typically, all events surrounding the christian Reformation movements are considered to be part of the early modern period.
    – ccprog
    Commented Oct 8, 2022 at 19:26
  • Thank you! I will look into this.
    – ghost
    Commented Oct 8, 2022 at 19:28
  • 3
    @ccprog As the question mentions the marriage between Mary of England and Philipp of Spain as potential example, I simply assumed that "medieval" was to be understood very liberally here.
    – Arno
    Commented Oct 8, 2022 at 20:45
  • It did work, just not right then
    – Richard
    Commented Oct 9, 2022 at 9:12

Think that in tipical medieval, feudal times, the King was just the primum inter pares (first among equals). He would not have direct control but over his own personal fiefdoms, for the rest of the country he would rely on the loyalty of other nobles that were his vassals (but, if those were powerful enough, could decide to ignore or even oppose him).

In this situation, usually the King would be unable to change the institutions, and the mobility would have wanted to keep their power.

So, the concept of "merging" kingdoms (or duchies, principalities, whatever) would be alien to those people. What you would have would be the same king holding simultaneously the titles to several entities, but each of them would remain separated. Spain it is a good example, after Isabel and Fernando the kings were always common, but the kingdoms of Castille and Aragon did exist, did have different institutions and laws, and each new king would need to be confirmed as king of each kingdom. And we are talking here about the Modern Age (with formal unification coming only after the Spanish War of Succession, 1714), when the power of kings was considerably increased in relation to the nobility.

As a result, kings and other nobles would amass long lists of titles covering all of their rights to the land they held (and some that they did not held but that they did claim), and that they had got through inheritance or conquest.

That does not mean that the nobility of a country would be uninterested in their king becoming king of other country, but it was... complicated. On one hand, it could mean that these nobles maybe could use the king's influence to get holdings in the new country. In the other hand, it could mean that the king could try to drag them into supporting his campaigns to defend his new kingdom. Or that the king could develop a new support base in the other country and use it to be less dependent on local nobility.

As a side note, perhaps the Polish-Lithuanian Commonwealth is a better study case, since as stated elsewhere, the "Spanish" personal union was too late to be considered medieval.

  • Lithuania was a Grand Duchy; so your final example is specifically excluded despite my attempts to have OP make a sensible extension of his question. Commented Oct 11, 2022 at 16:45

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.