To add to the previous answer, a nation-state defines a group of people with:
- a common language
- religion (although this isn't necessary, there can be many religions within one nation-state, but some examples, like Israel, fall under the category of a shared religion)
Within culture, you can include national literature, songs, food, etc.
Prior to nation-states, Europe had feudal manors that linked small towns and villages with a regional king, or even empires (i.e. the Holy Roman Empire [HRE] which formed and allied with the Roman Catholic Church after the fall of Rome with Clovis and his Franks settling into Northern Europe and later Charlemagne expanding the HRE over much of Europe). Once religious wars started to divide Europe and feudalism was no longer the link between separate towns, a need for political unity arose and nation-states, dividing those with common culture, language, religion, etc., began to define political Europe.
With the West African nation of Mali in the news over the past two years due to the strife involving Islamist extremists and French-backed government forces vying for control of important regions of the country, renewed focus has been placed on Mali’s history and significance. The insurgent occupation of the historic city of Timbuktu in early 2012 caused concern among societies in the West as well as in the Islamic world regarding the important artifacts stored in the city’s main mosque and universities, as Islamist extremists like the Taliban of Afghanistan have a practice of destroying important religious artifacts. Once a major cosmopolitan center of learning, Timbuktu was designated by the United Nations as a World Heritage Site, meaning its historical importance to mankind transcends political boundaries. Although symbolic, the designation does illuminate Timbuktu’s role in history.
The reason for this background on Timbuktu and Mali is to place in the proper context the significance of the rule Musa I of Mali (1280-1337), also known as Mansa Musa, or “Musa, King of kings.” During Musa I’s reign, he built Timbuktu into a center of Islamic learning and culture, as well as trade, during the 14th Century and incorporated the city into the Malian Empire over which he ruled. In short, it was his efforts that turned Timbuktu into the city that would, centuries later, be designated as a World Heritage Site. Musa I’s pilgrimage to Mecca, in current day Saudi Arabia, in 1324, established him as a major Islamic ruler, and he brought home from his pilgrimage a sense of devotion that manifested itself in the construction of the ornate mosques and universities central to Mali’s identification.
The modern concept of the nation-state has its origins in the Thirty-Years War of 1618 to 1648, which raged throughout Central Europe and was finally resolved with the signing of the Treaty of Westphalia. A conflict between Catholicism and Protestantism, that war, or, more precisely, that series of wars, pitted the Austro-Hungarian Habsburg Empire against France, Sweden, Holland and Denmark. In addition, the multitude of German principalities that then-existed provided another dimension to the warfare, with some supporting their Austrian brethren while others sided with France and the other opponents of the Habsburgs. While the Habsburgs faced numerous enemies during the 30-year time period in question, they weren’t all fighting at once. In actuality, participation among various countries occurred in a more phased or incremental fashion, with the French war against the Austrians providing the most climactic period of the wars, stretching as it did from 1634 until the war’s end. It was during this final phase of the war, particularly the last four years of the fighting, that negotiations to resolve the myriad disputes took root, and were finally concluded with the signing of the treaty, also referred to as “the Peace of Westphalia.”
The significance of this period lies in its institutionalization of the concept of the nation-state. Prior to the resolution of the Thirty-Years War, many political entities involved individual towns or cities, or, sometimes, regions. With the decline in the power and influence of the Catholic Church that was an outcome of the war, with the age of feudalism nearing its end, at least in Europe, and with a resurgent sense of a need to unify disparate political entities like towns and villages, especially with respect to boundaries incorporating communities of common ethnicity, the concept of the nation-state was formalized. The signing of the treaty is considered the birth of the modern system of international relations. Entire regions informally bound by common heritage were now formalized into larger political entities that enjoyed the legitimacy of those over whom they exercised sovereignty.