Imperialism often leaves more people outside a country than in it:

Apparently there are 43 million people in the United States who claim Irish ancestry. So if we believe that, Irish Americans outnumber Irish people by over eight to one. The latest Irish census puts the population at 5.5 million. We are all familiar with the Irish Famine in the 19th Century. Now apparently the Irish population before that disaster was 8.5 million and following the deaths of over one million from starvation and the emigration of at least another million if not two, the population was reduced to around three million. Irish emigrants to the USA prospered and spread the four corners of that land. Imagine though, outnumbering the original population by eight times? I’m sure that has to be a record even though there are vast ethnic German and Italian populations in the US also. It’s a fascinating story and I’ve written a book about it which I hope to publish later this year.

But enough about Ireland and the US - we are not the only country where our expatriate population outnumbers those at home. If we take it to extreme measures, the Kurdish people are the largest stateless ethnic group in the world. There are approximately 45 million Kurds: Most of them can be found in Turkey (20m) Iran (12m), Iraq (10m) and Syria, and of course in many other countries. I know many Kurdish people who live in Turkey and while they would love a homeland, they are not too bothered about it and are content to live as Turkish citizens where they say their ethnicity is respected and they are treated fairly. I have no knowledge of the situation in Iran and Iraq but it has been said that Kurds are not treated well there.

But this article stems from a conversation I had with an Azerbaijani person last week in which he told me that there are more Azerbaijanis in Iran than in their homeland. Azerbaijan has a population of 10 million people and he claims that there are another 30 million living in Iran. I did some research and his contention is based on a genuine historical reality, although the figure of 30 million is disputed.

There is no reliable modern Iranian census of ethnic groups, so nobody can give an exact number. Estimates vary considerably. Minority Rights Group currently puts the Azerbaijani population of Iran at around 16 percent of the country's population and says the group may number around 15 million. Other estimates go considerably higher, into the 20–25 million range and figures of 30 million are certainly widely quoted in Azerbaijan and elsewhere.

The outline of modern Azerbaijan shows how it is squeezed between Russia and Iran, hence large groups of ethnic Azerbaijanis are situated outside their homeland.

The history behind this is fascinating. The key point is that Azerbaijanis did not originally cross an international border into Iran. The modern border was imposed across a population that already lived in the region. For centuries, much of what is now northern Iran and the Republic of Azerbaijan formed part of the same broad political and cultural world.

The region was ruled at different times by Persian empires, Turkic dynasties and local khanates. The population included Persian-speaking and Turkic-speaking communities and the Turkic language that eventually became modern Azerbaijani became particularly important in the region.

Then, in the early nineteenth century, Russia began expanding southwards into the Caucasus. We are back to imperialism again. Of course it wasn’t just the British and the Russians – all major nations were at it. We can recall the Ottoman Empire (Turkish), the Austro-Hungarian, or the French, Spanish, Portugese, Dutch and even Belgian empires? To the south of Azerbaijan, the Iranians or Persians were at it also.

Russia fought two major wars against Qajar Persia, in 1804–1813 and 1826–1828.

The first war ended with the Treaty of Gulistan in 1813, which transferred a large number of territories in the South Caucasus from Persian control to Russia.

The second ended with the Treaty of Turkmenchay in 1828. That treaty was decisive. Russia acquired the Erivan and Nakhchivan khanates and established a border that ran broadly along the Aras River - in other words – modern day Azerbaijan. The important point is that the people living on both sides of the new border did not suddenly become different peoples.

The border was political. The population was not. Turkic-speaking Muslim communities found themselves divided between the Russian Empire to the north and Persia to the south. Over time, the northern part developed into what eventually became the Republic of Azerbaijan. The southern part remained in Iran.

So when an Azerbaijani today talks about ‘30 million Azerbaijanis in Iran,’ they are essentially saying, ‘We are one people who were divided by an imperial border." That is a very powerful idea in Azerbaijani national consciousness.

But there is an important qualification. The people living in northern Iran today are Iranian citizens, and many of them have a strong Iranian national identity as well as an Azerbaijani ethnic and linguistic identity. They are not simply Azerbaijanis who happen to live in another country.

Azerbaijani Turks have played an enormous role in Iranian history. They were particularly important in the Iranian Constitutional Revolution of 1906, and Azerbaijanis have also played major roles in Iranian politics, commerce, culture and the 1979 revolution. Minority Rights Group notes that most Iranian Azerbaijanis have historically identified with the Iranian state rather than seeking separation.

They are also predominantly Shia Muslims, like most of the population of the Republic of Azerbaijan. That religious connection is another reason the boundary between the two populations has never been as simple as the modern international border suggests. The geographical concentration is particularly striking. Iran's Azerbaijani population is concentrated mainly in the northwest and there are also very large Azerbaijani communities in Tehran and elsewhere in Iran.

There is also one other fascinating historical wrinkle. The word "Azerbaijan" itself has a complicated history. The territory south of the Aras River was historically associated with the name Azerbaijan as well. The modern Republic of Azerbaijan adopted that name when it became independent in 1918. So when we talk about ‘Azerbaijanis in Iran,’ we're talking about a population whose language and cultural identity developed across a region that was subsequently divided between two states.

This is why you will sometimes hear the terms North Azerbaijan and South Azerbaijan. "North Azerbaijan" generally refers to the territory of today's Republic of Azerbaijan. "South Azerbaijan" refers to the Azerbaijani-populated regions of northwestern Iran. The terminology is politically sensitive, however, because Iranian authorities obviously do not regard their Azerbaijani-populated provinces as some kind of unfinished part of the Republic of Azerbaijan.

And there is an important difference between ethnic identity and political allegiance. Most Iranian Azerbaijanis are not campaigning to join Azerbaijan. Many are perfectly comfortable being Iranian while speaking Azerbaijani at home and maintaining their own cultural traditions.

There may be thirty million of them or it might be fifteen, depending on what they choose to identify as. Trying to estimate how many there are is fraught with difficulty. The border between Iran and Azerbaijan was drawn by the Russian and Persian empires in the nineteenth century, and it divided an existing Turkic-speaking population.

In other words, just as Nagorno-Karabakh demonstrates how Soviet borders could put one ethnic population inside another republic, the Azerbaijan–Iran border demonstrates something even older: An imperial border can divide a people without actually dividing their language, culture or sense of identity. We only have to look at what the big European imperial powers did in Africa to appreciate this fact.