International relations (IR) from the mid-17th century to the mid-20th century were founded on the decisions by the Peace Treaty of Westphalia in 1648 that ended the Thirty Years War. However, from the beginning of the 21st century, the IR are once again more and more framed by the international standards established in 1648.
The Thirty Years War (1618−1648)
This (First Pan-European) war was a confessional-political conflict, in essence, between the Protestant and the Roman Catholic leaders with very catastrophic consequences in population losses and material destructions as, for instance, the German lands lost approximately one-third of its pre-war population with some regions depopulated up to 90%. From the late 16th century onward, Europe, especially her central part, was experienced by religious confrontations between, on one hand, the Roman Catholics, and, on other hand, the Protestants (the Lutherans, Calvinists, and Zwinglians), who seriously challenged the right of the emperor of the Holy Roman Empire to decide on their religion. It is estimated that almost 8 million people in Europe lost their lives during the war.
The war started in 1618 as a regional conflict between the Protestants and the Roman Catholics on the territory of the Kingdom of Bohemia within the Holy Roman Empire, but soon it involved the armies of the Habsburg Monarchy, the Kingdom of England, the Kingdom of France, the Kingdom of the Netherlands, the Kingdom of Spain, and finally the Kingdom of Sweden. More precisely, the conflict began when the Roman Catholic archbishop of Prague destroyed several Protestant churches. The Bohemian Protestants appealed to the emperor of the Holy Roman Empire to settle this issue, but his intervention did not satisfy the Protestants and the war started when the Protestants from the emperor’s palace in Prague committed the Second Defenestration in the Bohemian history (threw two emperor’s ministers out of a window, deposed the Roman Catholic king of Bohemia and elected as a new one the Protestant Frederick, elector of the Palatine). The struggle for the souls became in this war the focal reason for the combat regardless to the fact that in some cases the rulers have been much more interested in keeping their posts than to fight for the religious dogma. From the chronologic viewpoint, the war is divided into three periods:
- From 1618 to 1622.
- From 1623 to 1634.
- From 1635 to 1648.
The Roman Catholic emperor of the Holy Roman Empire, Ferdinand II (1619−1637) from the house of Habsburgs, up to 1623 was victorious in the war with a great help provided by Bayern (Bavaria) and the Habsburg Spain. However, Ferdinand’s political ambitions in the Central Europe and his military alliance with the Spanish branch of the Habsburg house provoked the revolt of the Protestant states of Europe followed by the Roman Catholic France as a traditional Habsburg’s enemy. Denmark became a leader of the Protestant league in 1625 which became, in fact, a coalition against the house of Habsburgs. After having been beaten in several battles by the Habsburg generals, Denmark’s army left the war by signing the Treaty of Lübeck in 1629 when Ferdinand II consolidated his power. A new moment in changing the balance of power came when a Protestant Sweden of the king Gustav II Adolf (1611−1632) joined the war. The war was ended on the lands of Germany by the Treaty of Prague (1635) with the Habsburg victory, but the Swedish and Dutch ally France joined the war against the Habsburgs in the same year to alter the destiny of the war once again. Therefore, it was not until France joined Sweden in 1635 that the tide of the war started to turn against Vatican’s sponsored Habsburgs as the main protectors of the Roman Catholicism in Europe. Subsequently, from 1635 the war lost much of its original religious character as for France it was not so much a religious struggle against Vatican and the Holy Roman Empire but rather a political conflict for power in Europe. The combined forces of France and Sweden were enough to overcome the armies of the Holy Roman Empire. The crucial disputes between the states engaged in the war became solved by the Peace Treaty of Westphalia (1648), but the war between France and the Habsburg Spain was finished only in 1659 by the Treaty of the Pyrenees.
The Peace Treaty of Westphalia (1648) and its Consequences for IR
After 30 years of bloody battles, massacres, and changing side in alliances, the Thirty Years War was ended on October 24th, 1648 by the Peace Treaty of Westphalia, which was signed twice at two different places: first at Münster and later at Osnabrück (i.e, in one the Roman Catholic city and one the Protestant city). The Treaty finally brought the Thirty Years War to the end and established a new system of IR based on its fundamental principle – the state’s sovereignty.
The Treaty is one of the most important documents in the history of Europe with details upon returning the occupied territories, information on wrong-doing events during the war, trade regulation after the war or the manner in which the armies would be disbanded and prisoners of war set free. As a most important political consequence of the war and the Treaty was that France became a dominant state in continental Europe. The Treaty established, nevertheless, the legal foundations for the modern system of IR, that is usually named as a states-system in which the only, or at least the main, political actors are the sovereign (independent) states.
The basic conclusions of the Treaty were:
- The Roman Catholic house of Habsburgs recognized the state’s independence of Switzerland.
- The Protestant United Provinces became separated from the Roman Catholic Spanish Netherlands.
- The Roman Catholic France secured its administration in Alsace and retained the bishoprics of Metz, Toul, and Verdun.
- The Protestant Sweden got West Pomerania followed by bishoprics of Bremen and Verden.
- The Protestant Brandenburg acquired East Pomerania and the archbishopric of Magdeburg.
- The principle „Cuius regio eius religio“ (from the 1555 Augsburg Peace Treaty) was confirmed.
- The full and unchallenged political sovereignty of the states was recognized, what practically meant that the Roman Catholic emperor of the Holy Roman Empire from the Habsburg dynasty could not turn his empire into the exclusively Roman Catholic state.
The 1648 Treaty of Westphalia established three focal principles in regard to IR:
- A sovereignty of the states, according to the standard of Rex est imperator in regno suo, what meant that the ruler is fully autonomous within his own domain, but not a subject to the political will of anyone else. The settlement recognized the absolute power of rulers and linked the personal/dynastic power to a specific territory – a sovereign state.
- Collective (European) Security with the fundamental task to maintain the peace among the key actors in IR. The concept is fluctuating from more practical but an unregulated and anarchical balance of power and an idea of more theoretical aim to establish a kind of regulated world government under the international law and accepted standards of acting.
- The balance of power, that indicates the relative distribution of power between the states either into equal or unequal shares. In principle, it refers to the situation in which no one state predominates over others, what means to the policy of a power equilibrium in IR under the assumption that unbalanced power is dangerous for the regional or global security.
All three of these focal principles remained as the foundations of global politics and IR up to 1945 and became revived after the Cold War in the updated form. The treaty marked the start of the modern system of IR between the states by legitimizing the governmental authority to be both the final and only sovereign administration over the inhabitants within the geographic-political borders of their own political entity (state). Such arrangement meant both that the government became a sole arbiter in the internal state’s affairs and that the other states did not have any right to interfere into the internal affairs and policy of another state (i.e., to „cross the borders“ of the others). In essence, to be a sovereign (i.e., independent) political entity (state) meant two crucial features for the state’s administration:
- To live according to your own legislation (to be autonomous – in Greek, auto = self and nomos = law).
- To arrange your own internal affairs by yourself, i.e. without interference from outside, that meant, in fact, to be independent of all others, what presumed to possess supreme political authority within your own territory.
These principles of sovereignty inflicted a strong blow to the Roman Catholic Church in Vatican and its head (pope), as it meant that the European monarchs were able to decide in full independence all matters of their own domestic (home) affairs, like the official state’s religion (Cuius regio, eius religio), free from any outside intrusion. The 1648 Peace Treaty of Westphalia brought a new political order in Europe fundamentally based on the state’s sovereignty and independence of their rulers who received the rights to maintain standing armies, build defense fortifications, and collect taxes from their subjects. The principle of state’s sovereignty was later, by the Treaty of Utrecht in 1713, finally consolidated „by linking sovereign authority to a fixed territorial boundary“.
By the introduction of the principle of sovereignty, the governments of one state stopped to support their co-religionists in conflict with the rulers of other states as the policy of non-interference into the inner affairs of other political subjects became a sacral. Therefore, the practice of extraterritorial authority of Vatican was severely weakened in the Roman Catholic states, while in the Protestant states it was totally abolished. As a consequence, the states were becoming more and more secular national-states, instead of previously theocratic. It meant, as well as, that the citizens with both duties and rights replaced the subjects with only duties within the state’s borders. The meaning of sovereignty itself was gradually shifting from a single power by inherited ruler (dynastic sovereignty) over the state to the commonwealth, or popular power, by elected people’s representatives. The royal council (advisory institution) was replaced by the parliament (legislative institution), government (executive institution), and court (justice institution). A formal recognition of state’s sovereignty (like the establishing of diplomatic relations) applies and de facto acceptance of the moral or/and a legal validity of the acts issued by the „legitimate“ central administrative power of the recognized state.
A new Westphalian System of IR (WSIR) established the principle of Collective Security (CS) as the peace treaty of 1648 provided that in the case of the aggression by one or several states toward another one(s), all other states have to adopt a common policy of the restoration of the status quo before the aggression, i.e. before the violation of the borders of a sovereign state by another one(s). In other words, WSIR required a common action in order to secure the European or/and global security in which an agreement was reached between a group of states (in principle Great Powers – GP) to act as an unified opposition to any member state that illegally violates the peace by the act of aggression.
The principle of state’s sovereignty promoted in 1648 became soon the crucial pivot for the creation of the national-states, first across Europe and later around the world. The essence of modern national-state became the Westphalian idea that political legitimacy has to come from secular legal authority rather than from divine sanction as it was a practice in the Middle Ages. This is how the way to the constitution (supreme law collection) and constitutional government was paved by the Peace Treaty of Westphalia, which also helped the monarchs to consolidate the power over the state’s territories for the sake to obtain greater manpower and financial resources needed to strengthen the armies. Therefore, a modern system of taxation and tax-collections was introduced followed by the policy of imperialism for the matter of exploitation of overseas colonies. The creation of big and powerful armies accompanied with the efficient taxation system as well as required and functioning of more stable state’s organization based on a centralized administration and its bureaucratic apparatus. Therefore, it became quite necessary to shift the activity of the state from kingship to government. In other words, the consequences of the Thirty Years War inaugurated the modern national-state by the Peace Treaty of Westphalia.
The Fundamental Elements of Sovereign Equality between the States
Basically, up today global security and IR are formally shaped, with some cosmetic modifications after 1945, according to the ideas of the Peace Treaty of Westphalia in 1648, which established principles of sovereignty of each independent state and collective security that was protected and re-shaped by GP regardless to the very practical problem that both sovereignty and collective security are in fact contradictory principles. Nevertheless, the fundamental principle of collective security is that all (GP) states are encouraged to unite their policies and forces against any aggressor state that means against the state which violated the borders of another one. However, at the same time, the principle of sovereignty implies the fact that other states do not have legal right to interfere into the internal affairs of any other state, at least without direct legal permission by some authorized supranational organization (the UNO).
According to international law, all sovereign states are equal, what presupposes that sovereign equality has to be the foundation upon which some supranational security organization (the League of Nations or the UNO) operates. This principle of equality of sovereignty of all states as political actors in IR is formally giving the guarantees of equal participation in global politics, and such proclaimed sovereign equality has the following principal elements:
- All states are legally equal on the international scene and in relations to each other, regardless of their size, manpower or economic or military might.
- Every state enjoys the same rights inherent in full sovereignty’s meaning.
- Every state is under full obligation to respect the legal entity of another state including and territorial integrity.
- The territorial integrity, state’s borders, and political independence of a recognized state as a sovereign political actor are inviolable unless the action is sanctioned by the supreme international security authority (the UNO or similar).
- Every sovereign state has a full and unrestricted right to develop its own political, social, economic, and cultural systems without the interference from the outside.
- Each state is obliged to carry out a full range of all accepted international obligations as an equal member of international community of equal sovereign states.
- Every state has an obligation to live in peace with all other states.
 Steven L. Spiegel et al, World Politics in a New Era, Belmont, CA: Wadsworth/Thomson Learning, 2004, 150.
 About the Thirty Years War, see [Richard Bonney, The Thirty Years’ War 1618−1648, Oxford: Osprey Publishing, 2002; Peter H. Wilson, The Thirty Years War: Europe’s Tragedy, Cambridge, MA: Belknap Press of Harvard University Press, 2011].
 The German lands needed up to next two hundred years period in order to recover themselves from the effects of the war, which was one of the bloodiest in the European history. However, the Thirty Years War brought the Middle Ages to end and significantly undermined the political power of the Vatican’s coalition: the pope, the Habsburgs and the Holy Roman Empire.
 This peace agreement was composed by several treaties that confirmed the independence of the states within the Holy Roman Empire, and, subsequently, allowed their monarchs to choose their own religion (the Roman Catholicism or a form of Protestantism).
 About the Peace Treaty of Westphalia, see [Derek Croxton, Anuscha Tischer, The Peace of Westphalia: A Historical Dictionary, Westport, CT: Greenwood Publishing Group, Inc., 2001; Derek Croxton, Westphalia: The Last Christian Peace, New York: Palgrave MacMillan, 2013].
 The principle Cuius regio, eius religio confers upon the ruler the real power to determine which religion (the Roman Catholicism or any Protestant form) is going to be practised in his domain. That was a principle which prohibited any interference in the internal affairs of other states on religious grounds. This principle is even today very important as it provides the foundations for international law [Martin Griffiths, Terry O’Callaghan, Steven C. Roach, International Relations: The Key Concepts, Second edition, London−New York, Routledge, Taylor & Francis Group, 2008, 247]. It has to be noticed that international law is the law which governs all actors in international affairs, and it is divided into private and public segments. Private international law is regulating international activities carried out by individuals and all other non-state actors on the international arena. Public international law is applied to the states as legal subjects and, therefore, is dealing with the relations between the governments [Andrew Heywood, Global Politics, London−New York: Palgrave Macmillan, 2011, 332].
 To define aggression is in the academic discipline of global politics and IR extremely contested issue mainly for the reasons that different definitions will provoke different practical political implications and consequences. There is, however, a minimal level of common consensus in this case as the aggression is commonly understood as „a premeditated attack by one actor on another, but there agreement ends“ [Richard W. Mansbach, Kirsten L. Taylor, Introduction to Global Politics, Second edition, London−New York: Routledge, 2012, 316]. Two classical examples of the aggression act, according to such understanding of the term, would be: 1. The Israeli attack on the neighboring Arab states in June 1967, and 2. The NATO’s bombing of Serbia and Montenegro in 1999 (March−June).
 The case of the NATO’s aggression on Serbia and Montenegro in 1999 is the best example of the flagrant violation of this principle.
 Martin Griffiths, Terry O’Callaghan, Steven C. Roach, International Relations: The Key Concepts, Second edition, London−New York, Routledge, Taylor & Francis Group, 2008, 299−300. However, the states lost the certain degree of sovereignty by entering the arena of IR as they have to accept common duties and obligations fixed by the international community, which are, in fact, restricting their real independence.