Did it happen that a sovereign country voluntarily decided to become territory of another country? By voluntarily I mean it could have had the choice to say no. Even better if the joining country was the one who initiated the process.

  • The Anschluss of Austria did include a vote where the Austrians voted to join Germany, but I wouldn't really count it, as Germany was applying a huge pressure and Hitler would have been unlikely to take "no" as an answer.
  • The unification of Germany and Italy in the late 19th century would be better examples, but they also have their issues: in both cases it was one stronger country conquering the others, even if by diplomatic pressure instead of military force in many cases.
  • The closest I could find was the Republic of Texas, but there are some issues. It was just a very short-lived temporary country which just broke away from a country, and soon joined another one. It was diplomatically recognized by quite few countries.

Were there examples with more established countries who voluntarily choosed to become part of another country, or even better, initiated this by themselves without an imminent threat of being invaded?

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    I think there are quite a few examples. The Acts of Union between england and scotland. The Swiss confederacy.
    – Colin
    Commented Sep 18, 2016 at 19:59
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    Plenty of former HRE states joined Prussia as it progressed towards Germany's unification. Commented Sep 18, 2016 at 20:12
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    I was going to suggest Hawaii, but apparently it wasn't voluntary. Now if you'll excuse me, I need to brush up on my history. :-\
    – pr1268
    Commented Sep 18, 2016 at 23:02
  • Yes, Prussia did not "conquer" Germany. Bismarck first united the North against Austria and then the war with France provided for the union with Southern states. Note that the states continued to exist within the German Empire
    – SJuan76
    Commented Sep 18, 2016 at 23:50
  • I wonder would the Teutonic State of Prussia becoming the Duchy of Prussia count, or the way the personal union between Brandenburg and Prussia becoming effectively a single entity before Prussia became an independent kingdom? Both have a lot of murky areas but they seem to fit the criteria as the HRE wasn't really a functioning empire
    – Kate Paulk
    Commented Sep 19, 2016 at 11:51

16 Answers 16


[Re-edited to include various suggestions from comments and other answers]

We can divide the answer into two sections, the first of which addresses the general question of voluntary mergers between sovereign countries which create new countries, and the second the more specific question sovereign countries voluntarily becoming subsets (states, provinces, protectorates, etc.) of other countries.

1. Mergers

There are a number of examples. This Wikipedia page has a decent list of proposed unions (successful and not). Eliminating the cases of coercion and conquest and also the failed or short-term cases, there are, at a minimum:

I'm excluding the various unions of different territories as a result of dynastic marriages that took place prior to the modern era in many parts of the world, on the grounds that it's hard to consider most of those marriages "voluntary". One possible case is the personal union of Castile and Aragon via the marriage of Isabella and Ferdinand, since this was a secretly conducted voluntary marriage (they basically eloped!) between heirs who became rulers of their respective kingdoms.

There were also various sorts of pre-modern leagues and associations, the most enduring of is probably the Swiss Confederation (which eventually became a recognized country in its own right). It's a bit hard to know how to classify some of these, since the "sovereignty" of the various constituents was often ambiguous. (As a relatively recent example, the Swiss canton of Neuchâtel was technically ruled by the King of Prussia up until the 1848 revolutions, and he didn't give up his claims until 1857.)

2. Joining as subordinate territory

This involves cases where one country decides to joins a second country as one or more states, provinces, protectorates, etc. of the latter. A non-exhaustive list:

There are other events which, on the face of it, involved a sovereign state joining another state, but these tend to involve temporary or puppet regimes of one kind or another which make the "voluntary" part rather dubious (e.g., the annexation of Hawaii by the US; the annexation of Tannu Tuva by the Soviet Union).

(I'm also not counting cases of non-sovereign states where the electorate chose union with another state after being ruled by a third country, without ever first really being at least nominally sovereign, such as Saarland and Hatay.)

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    East and West Germany is unfair. They merged almost as soon as the powers that were preventing it became too weak to do so.
    – Joshua
    Commented Sep 18, 2016 at 23:44
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    I was going to add that the Dominion of Newfoundland voluntarily joined Canada in 1949, but I see you already got that one.
    – user19577
    Commented Sep 19, 2016 at 1:54
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    If you are including the formation of the US then the federation of the Australian colonies on 1/1/1901 is a candidate as well. Technically, they were not sovereign nations but self-governing British dependencies, however, so were the American colonies.
    – Dale M
    Commented Sep 19, 2016 at 5:24
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    @Bregalad: Since the union of Norway and Sweden took place after a Swedish invasion (and an international treaty forcing Denmark to cede Norway to Sweden), I'm not sure it really counts as "voluntary" (the Norwegians seem to have wanted to be independent of both Denmark and Norway). Commented Sep 19, 2016 at 10:49
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    @DaleM: The difference, I think, is that at the time the US formed under the Articles of Confederation (1776-1781), the states had declared themselves sovereign and independent from Britain. After 1783, even Britain recognized their independence, so the "re-assembly" under the Constitution in 1788-1791 clearly did not involve "self-governing dependencies of Britain". Commented Sep 19, 2016 at 10:58

Attalus III Philometor, 133 BC, leaves his kingdom to Rome.

The Wikipedia article on Attalus III has very little more to add.

Was this voluntary? There was an uprising following the occupation by Rome, with support of the neighboring kingdoms. One neighbor, Mithridates V, was a Roman ally, though he may have been playing a double game; certainly his son was doing so during his long reign.

More detail is found in the History of Rome, Vol. IV, p. 317


During this time Attalus Philometor, of Pergamus, had died, and with him the dynasty of the princes of Pergamus had become extinct. The first princes of that family were clever men, and of a mild disposition, although much may be said against their policy, if we take humanity as our standard. But the last Attalus was a man of different character: his reign was tyrannical, and he himself was one of those contemptible miscreants whom we meet with occasionally in the history of the East, where a little natural perversity is easily carried to the highest pitch, as in the case of the gluttony of Sultan Ibrahim. In the East, men sometimes take a delight in what is most unnatural and disgusting, and thus become true incarnations of a base and satanic nature. Such a man was Attalus. The only art he occupied himself with, was that of preparing poisons; and what amused him most was, to get rid of those who were his nearest in kindred. He died without issue, and left his whole kingdom to the Romans, who certainly would not easily have recognised any one else as his successor; for they looked upon his kingdom as their own property, which they had a right to claim, just as a master had the right of succession to the estate of his slave or his freedman, who died without having made a will. The remarks of Florus, therefore on this affair are foolish. But there was a natural son of Eumenes, the predecessor of Attalus, called Aristonicus, who claimed the kingdom of Attalus as his lawful inheritance; as however, there was no one in the world who could give him assistance, it is inconceivable how he could have the madness to believe that he would be able to hold out against the Romans, and how it was possible for him to find any support among the people of Pergamus. And yet the war lasted much longer than had been anticipated. The effeminate inhabitants of the magnificent country of Lydia and Ionia carried on the war with great resolution; and besides them, Aristonicus had many Thracian mercenaries in his army. On the part of the Romans, the war was badly conducted, as their generals thought of nothing else but enriching themselves, and turning everything into money, instead of making the proper use of their victories: they were, in fact, glad when a powerful and wealthy town revolted, because it afforded them an opportunity for plunder. The war was at length brought to an end by M. Perperna and M.' Aquillius. Aristonicus was taken prisoner at Stratonicea, and adorned the triumph at Rome. The Romans thus acquired an extremely rich province. The end of this, as well as of the Servile war, belongs to a later date than the year 619, which is the year of the tribuneship of Tib. Sempronius Gracchus. The reduction of Sicily falls in the year 620, and the defeat of Aristonicus in 622.

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    I don't like this example since a 2000 years ago kingdom is not akin to what we call these days a country and it's also lacking on the voluntarily part, I bet the "people" weren't part of this volunteering. All in all, if this example pass then there are plenty of kingdoms that were annexed by larger kingdoms without a war. one that pops in my mind is Aragon and Catalonia.
    – Ezra
    Commented Sep 18, 2016 at 20:58
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    @Ezra: the OP didn't specify a time period, nor conditions on popularity of the event with the common people. Commented Sep 19, 2016 at 0:13

United Arab Republic = Egypt + Syria

The United Arab Republic (UAR) was a short-lived political union between Egypt and Syria, from 1958 to 1961.

The UAR membership in the United Nations replaced the memberships of both Egypt and Syria.

  • I wonder how much practicality was in it, was there a real free movement? some consolidation of their security forces? law? currency?
    – Ezra
    Commented Sep 19, 2016 at 5:21
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    @Ezra the idea was to unite all the Arab countries in the ME under one flag, reestablishing the Khaliphate under a single Muslim Arab state. It never got there of course. IS by now is trying to achieve much the same thing through other means. It's a dream among Muslims that's been smouldering for centuries and resurfaces every few decades.
    – jwenting
    Commented Sep 19, 2016 at 7:02
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    @jwenting The characterization of the UAR as "Khaliphate" may be missleading, since the people in power both in Egypt and Syria were secularists. Their were not pro-West, but they were clients of the SU and their discourse was not religious but anticolonialist.
    – SJuan76
    Commented Sep 19, 2016 at 12:47
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    @jwenting: Saying the UAR (and the pan-Arabic ideology behind it) were trying the "reestablish the Caliphate" is like saying that the EU is trying to reestablish the Holy Roman Empire. The modern founders of Syrian Pan-Arabism in the 1930s, for example, included two Christians and an atheist (Constantin Zureiq, Zaki al-Arsuzi and Michel Aflaq). Commented Sep 19, 2016 at 14:25
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    @jwenting - I'd still consider that very sloppy terminology. There was no attempt to install a Caliph, nor any intention of doing so, and no attempt to involve non-Arab Muslims (eg: The Turks, who actually held the previous Caliphate). The word "Arab" in the name should be a big clue that the founding concept was ethnic, not religious.
    – T.E.D.
    Commented Sep 22, 2016 at 20:24

How about the Dominican Republic inviting Spain to retake administration in 1861?

The Dominican Republic has a complicated history that involves 3 attempts to voluntarily join another country. They won independence from Spain in 1822 and immediately joined Haiti. Then they won independence from Haiti in 1844, but 17 years of misrule led to an economic mess that the last president thought Spain could bail them out of. The re-occupation didn't go so well either, and they reasserted independence in 1865.

The new administration still wanted to hand over power to a bigger country, and tried to get the United States to take over, but the measure failed in the US Senate. That was probably all for the best, since the idea doesn't seem to have had popular support in the DR. The Dominican Republic has remained independent ever since.

  • (+1) A minor quibble, I am not sure I understand your parenthesis correctly but Haiti won its independence from France in 1804. It wasn't freed or conquered in 1822 but occupied the newly independent Spanish part of the island (i.e. the Dominican Republic).
    – Relaxed
    Commented Sep 21, 2016 at 12:47
  • @Relaxed That's not a minor quibble; it's a blunder on my part. I tried to clean it up a bit.
    – Xerxes
    Commented Sep 22, 2016 at 19:33

It is interesting most people seem to only study/remember European history.

Panama joined Colombia in its early years after it declared independence from Spain. They formed New Granada. For a while Colombia and Venezuela were joined as well forming the Grand Colombia in which the great Simon de Bolivar was president.

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    Was Panama an actual independent country before joining Gran Colombia? The dates I have found that Panama got the independence and joined Gran Colombia exactly the same year, which makes it unclear if it "joined" Gran Colombia or if it was part of Gran Colombia from the beginning. In fact, from googling you get that Panama declared independence on 10 Nov 1821 and Gran Colombia was stablished in 17 Dec 1821... less than two months, way too short to state that it were "a sovereign state joining another" (and that is without talking about the issues of international recognition).
    – SJuan76
    Commented Sep 20, 2016 at 18:37
  • so one month of sovereignity doesn't count as being sovereign? Legality of any business contract, treaty, or agreement is not perceived as being invalid just because only one month has passed. Panama was a very young country and feared Spain was about to violently oppose their declaration of independence. Spain was obviously illegally controlling countries in this new 'discovered' continent. Panama was simply reaffirming the independence and freedom they had prior to Spain invading it. International recognition or approval is not needed when a country decides to free itself.
    – edwinc
    Commented Sep 22, 2016 at 6:10
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    Sovereignty is a more complicated affair than a business contract, because there is no well defined standard for it. Sovereignty is a fuzzy affair involving control of territory, international recognition and the structures of a states (government, judiciary, etc.). The facts that the declaration of independence and the petition to join Grand Colombia were the same day and that the union was effective less than a month later makes it difficult to test some of the above issues, since there was not enough time for international recognition or the development of the state.
    – SJuan76
    Commented Sep 22, 2016 at 7:12
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    In case that there is any confusion, please let me say that my doubts about when we should consider Panama to have become an independent state are not meant to show any kind of disrespect of Panama or its people; the discussion if Panama should be considered a sovereign state since 1821, 1903 (USA backed independence of Colombia) or other date does not affect at all its current status as a sovereign nation.
    – SJuan76
    Commented Sep 22, 2016 at 7:36
  • Good, interesting answer. I also have a South American example, below.
    – Tom Au
    Commented Sep 22, 2016 at 19:37

I think that the joining of Tanganyika and The People's Republic of Zanzibar and Pemba would fit your criteria. They changed the new country's name to Tanzania.


As I was born in and live in Saarland, I also would like to add the history of our small "country": we were separated from Germany twice (1919 and 1947) and formed a more or less independent country with close economical connections to France. But in both occasions, "we" (our predecessors) essentially voted to re-join Germany (in end-1934 and in 1955).


I think East Germany could be considered to fit your question. It was annexed voluntarily by West Germany in 1990. It was called unification but for all practical reasons it was an annexation.

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    One could argue that a new state emerged (or an old one was re-established), rather than a small country giving up its independence. West Germany was economically stronger, but why would it indicate that it was East Germany who joined the other and not vice versa? But my bad of not including it in my list in the question. I was imagining a smaller country giving up its independence without changing the joined country into something too different.
    – vsz
    Commented Sep 18, 2016 at 20:03
  • I think that what you're looking for is a nation voluntarily assimilating into another nation, which is quite contradicting to the nation state nature. Even so, east Germany in the eyes of some was a different nation and if west Germany wasn't economically superior to east Germany then their voice, I speculate, would have resonated with much more people making the unification less feasible.
    – Ezra
    Commented Sep 18, 2016 at 20:08
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    @vsz Legally, that's what it was and how it's called (Beitritt is still used in some contexts). All the laws and the constitution of West Germany remained valid and extended to the new territory. A precious few East German laws were reenacted on a local level and that's it. Note that it was actually debated at the time, creating a new state was precisely the vision the creators of the fundamental law of West Germany had (article 146). But in 1990 it was decided to use article 23 instead (and then to remove it to signify that no further extension was expected; article 23 is now about the EU).
    – Relaxed
    Commented Sep 18, 2016 at 22:21
  • @Ezra: In the view of West Germans there was only one German Nation. Commented Sep 19, 2016 at 18:26
  • @MartinSchröder and I'm sure that's how most of East Germans thought but I'm suggesting that there were many incentives for this point of view, which without them it's not obvious that this shared nationality would have existed. I think that we're seeing a similar process where smaller nations like the baltic states for example are incentivized to trade their local identity with a European one.
    – Ezra
    Commented Sep 19, 2016 at 18:51


In 1975, the Prime Minister of Sikkim appealed to the Indian Parliament for Sikkim to become a state of India. In April of that year, the Indian Army took over the city of Gangtok and disarmed the Chogyal's palace guards. Thereafter, a referendum was held in which 97.5 per cent of voters supported abolishing the monarchy, effectively approving union with India. On 16 May 1975, Sikkim became the 22nd state of the Indian Union, and the monarchy was abolished.

Source: Sikkim (Wikipedia).

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    Didn't Sikkim become a protectorate of India in 1950? Commented Sep 19, 2016 at 11:34

Following the lines Peter Erwin's answer, I think the EU should also be considered.

Legally, a country that joins the EU gives up on many aspects of its sovereignty to the new EU entity which is in practice mostly led by Germany and the other big western nations.

For the identity dynamics, which is I what I believe is in the essence of this question, many small countries are exchanging their old nationality with a European one which is again mostly defined by the big western nations.

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    The UK says that you are wrong... :-p
    – SJuan76
    Commented Sep 18, 2016 at 23:52
  • Initially the UK was a founding member. Hard to see what has changed but Great Britain and "Splendid Isolation" generally go hand to glove with Europe...and yet security wise that still remains untrue. The most spectacular example I would say was the USSR under Lenin. That guy really had a vision that a lot of people wanted in on. Stalin went a long way towards making the Soviet "Union" highly contradictory however...going so far as to call for a defense of the Motherland when the Nazi's invaded just as the Tsars had during Napoleon. Commented Sep 19, 2016 at 2:28
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    @user14394 The UK was not a founding member of the EU.
    – nvoigt
    Commented Sep 19, 2016 at 6:03
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    @nvoigt The UK was one of the twelve founding members of the EU in 1993. It was not however a founding member of the EEC that preceded it.
    – rojomoke
    Commented Sep 19, 2016 at 6:49
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    The EU at least tries to consist of sovereign states tightly bound by treaty obligations. To take a far "smaller" example, ICAO asserts that signatories retain complete sovereignty over their airspaces, even though they've agreed to enact certain laws and to allow foreign flights access to their sovereign territory. The EU goes a lot further in challenging us to define how treaty-bound a state can be before it is no longer "sovereign" in practice. In principle as long as an EU state still has its own government with the power to leave the EU and resume all authority, it's sovereign. Commented Sep 19, 2016 at 14:08

Ossetia the Russian Empire, Tuva joined the USSR.

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    How voluntary was it?
    – vsz
    Commented Sep 19, 2016 at 7:40
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    As near as I can tell, the short story on both was that they were playthings of the great powers of their era (Persia/Ottomans/Russia in the former case, and Mongolia/China/Russia in the latter), and Russia happens to have been the latest power to take them. There isn't much text on the mechanics in the first case. In the latter, the Communist government that gave up sovereignty had just come to power 5 years earlier in a Soviet-backed coup. So not really.
    – T.E.D.
    Commented Sep 19, 2016 at 18:30

In 1963 Singapore and the Federation of Malaya merged to form Malaysia. Singapore became independant again in 1965.

Source: History of Singapore (Wikipedia).

  • But Singapore was not a sovereign country at that time was it? The primary objective of joining Malaysia was to gain independence from the British.
    – slebetman
    Commented Sep 21, 2016 at 7:39

One possible example was the temporary Peru-Bolivian Confederation of the late 1830s.

Peru and Bolivia had been "one territory" during the colonial era, but became separate countries during the wars of independence. After a brief war between the two countries, Peru's General Gamarra and Bolivia's General Santa Cruz agreed that the two countries should be re-united. Peru was the larger (populationwise) and stronger of the two countries, so it was more eager for a union, or at least a Confederation, in the earlier days.

Then "Peru" subdivided into North and South Peru, leaving Bolivia the strongest of the three parties, and General Santa Cruz nominally the head of the whole "country". That was not so acceptable to the Peruvians, especially the North Peruvians. These people sided in a new war with neighboring Chile and Argentina against Bolivia and "South" Peru. General Gamarra reunited the two Perus and ousted General Santa Cruz from the newly reunited country with foreign help, so Bolivia went its separate way, and Santa Cruz went into exile


The Far Eastern Republic (though not widely internationally recognized) joined Soviet Russia in 1922, and was completely integrated into the country. The merger was voluntary as the government has been a puppet of Russia anyway, but I guess the people very definitely did not want to remain separated from Russia.

Even the creation of the Soviet Union itself qualifies - merger of Russia, the Transcaucasian SFSR, Ukraine and Belorussia has been voluntary in the sense that their ruling governments approved the union, and people were not against (re)integration with Russia that much, though they might have quibbles with the current government and ruling party.

  • "The merger was voluntary as the government has been a puppet of Russia anyway" - well... Commented Nov 10, 2016 at 8:53

I'm surprised no one has brought this up, although the concept itself was a bit odd to me.


The 1956 Mollet proposal is the particular instance I'm thinking of, even if it was knocked back.

  • 1
    Welcome to History SE. Please summarize the contents of the link and explain how it answers the question.
    – Rathony
    Commented Sep 19, 2016 at 10:14
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    I think the OP was asking for things that actually happened, not prospective unions or annexations that never took place. Commented Sep 19, 2016 at 10:59

If we include Texas and Hawaii we could also mention the Republic of Crimea. There are similar quibbles about the legitimacy of these annexations. Western governments and their corporate and state media scoffed at the overwhelming vote for accession, but subsequent polls sponsored by the Canadian, German and US governments found consistent results, see Do the Crimean people prefer to be with Russia than with Ukraine?.

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    Well... the Republic of Texas existed for about ten years before annexation (and was recognized by France and several other countries), and Hawaii was an independent kingdom before the coup d'etat, and the Republic of Hawaii existed for about four years before annexation. Whereas the "Republic of Crimea" technically existed for about a single day, so I don't think they're comparable. Commented Sep 19, 2016 at 15:07
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    I don't think you can count that as "voluntary", (and yes, perhaps Hawaii as well) as the Republic in question only discovered its desire to join the other country after troops of that country occupied it. The best historical comparison I know of for this is the Anschlus plebiscite in Austria in 1938
    – T.E.D.
    Commented Sep 19, 2016 at 15:47
  • Sorry, -1 for reasons given in the comments. Commented Nov 10, 2016 at 8:53

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