Balance of power (international relations) in the context of "Defensive realism"

The revolutions of 1989, also known as the fall of communism, were a wave of liberal democratic movements that resulted in the collapse of most Marxist–Leninist governments in the Eastern Bloc and other parts of the world. This wave is sometimes referred to as the "autumn of nations", in reference to the revolutions of 1848 as the "spring of nations". The revolutions of 1989 were a key factor in the dissolution of the Soviet Union—one of the two superpowers—and abandonment of communist regimes in many parts of the world, some of which were violently overthrown. These events drastically altered the world's balance of power, marking the end of the Cold War and beginning of the post-Cold War era.

The earliest recorded protests, which led to the revolutions, began in Poland on 14 August 1980, the massive general strike which led to the August Agreements and establishment of Solidarity, the first and only independent trade union in the Eastern Bloc, whose peak membership reached 10 million. The main region of the 1989 revolutions was Central Europe, starting in Poland with the 1988 Polish strikes, and continued in Hungary, East Germany, Bulgaria, Czechoslovakia, and Romania. On 4 June 1989, Poland conducted the first elections that led to the dissolution of the communist government, with Solidarity winning an overwhelming victory, leading to the peaceful fall of communism in Poland. Influenced by Poland, Hungary organised round table-format talks and began dismantling its section of the Iron Curtain. In August 1989, over a quarter of the Baltic states population physically chained for 675 kilometres (419 mi) in the Baltic Way protesting the occupation by the Soviet Union, while the opening of a border gate between Austria and Hungary set in motion a peaceful chain reaction, in which the Eastern Bloc disintegrated. This led to mass demonstrations in cities of East Germany and the fall of the Berlin Wall in November 1989, which served as the symbolic gateway to German reunification in 1990. A feature common to these developments was the extensive use of campaigns of civil resistance, demonstrating popular opposition to the continuation of one-party rule and contributing to pressure for change. Romania was the only country in which citizens and opposition forces used violence to overthrow its communist regime, although Romania was politically isolated from the rest of the Eastern Bloc.

Realism, in international relations theory, is a theoretical framework that views world politics as an enduring competition among self-interested states vying for power and positioning within an anarchic global system devoid of a centralized authority. It centers on states as rational primary actors navigating a system shaped by power politics, national interest, and a pursuit of security and self-preservation.

Realism involves the strategic use of military force and alliances to boost global influence while maintaining a balance of power. War is seen as inevitably inherent in the anarchic conditions of world politics. Realism also emphasizes the complex dynamics of the security dilemma, where actions taken for security reasons can unintentionally lead to tensions between states.

World War I, or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a global conflict between two coalitions: the Allies (or Entente) and the Central Powers. Major areas of conflict included Europe and the Middle East, as well as parts of Africa and the Asia-Pacific. The war saw important developments in weaponry including tanks, aircraft, artillery, machine guns, and chemical weapons. One of the deadliest conflicts in history, it resulted in an estimated 30 million military casualties, and 8 million civilian deaths from war-related causes and genocide. The movement of large numbers of people was a major factor in the deadly Spanish flu pandemic.

The causes of World War I included the rise of the German Empire and decline of the Ottoman Empire, which disturbed the long-standing balance of power in Europe, the exacerbation of imperial rivalries, and an arms race between the great powers. Growing tensions in the Balkans reached a breaking point on 28 June 1914 when Gavrilo Princip, a Bosnian Serb, assassinated Franz Ferdinand, the heir to the Austro-Hungarian throne. Austria-Hungary blamed Serbia, and declared war on 28 July. After Russia mobilised in Serbia's defence, Germany declared war on Russia and France, who had an alliance. The United Kingdom entered the war after Germany invaded Belgium, and the Ottoman Empire joined the Central Powers in November. Germany's strategy in 1914 was to quickly defeat France before transferring its forces to the east, but its advance was halted in September, and by the end of the year the Western Front consisted of a near-continuous line of trenches from the English Channel to Switzerland. The Eastern Front was more dynamic, but neither side gained a decisive advantage, despite costly offensives. Italy, Bulgaria, Romania, Greece and others entered the war from 1915 onward.

A buffer state is a country geographically lying between two rival or potentially hostile great powers. Its existence can sometimes be thought to prevent conflict between them. A buffer state is sometimes a mutually agreed upon area lying between two greater powers, which is demilitarised in the sense of not hosting the armed forces of either power (though it will usually have its own military forces). The invasion of a buffer state by one of the powers surrounding it will often result in war between the powers.

Buffer states, when authentically independent, typically pursue a neutralist foreign policy, which distinguishes them from satellite states. The concept of buffer states is part of a theory of the balance of power that entered European strategic and diplomatic thinking in the 18th century. After the First World War, notable examples of buffer states were Poland and Czechoslovakia, situated between major powers such as Germany and the Soviet Union. Lebanon is another significant example, positioned between Syria and Israel, thereby experiencing challenges as a result.

The Peace of Utrecht was a series of peace treaties signed by the belligerents in the War of the Spanish Succession, in the Dutch city of Utrecht between April 1713 and February 1715. The war involved three contenders for the vacant throne of Spain, and had involved much of Europe for over a decade. Essentially, the treaties allowed Philip V (grandson of King Louis XIV of France) to keep the Spanish throne in return for permanently renouncing his claim to the French throne, along with other necessary guarantees that would ensure that France and Spain should not merge, thus preserving the balance of power in Europe.

The treaties between several European states, including Spain, Great Britain, France, Portugal, Savoy and the Dutch Republic, helped end the war. The treaties were concluded between the representatives of Louis XIV of France and of his grandson Philip on one hand, and representatives of Queen Anne of Great Britain, King Victor Amadeus II of Sardinia, King John V of Portugal and the United Provinces of the Netherlands on the other. Though the king of France ensured the Spanish crown for his dynasty, the treaties marked the end of French ambitions of hegemony in Europe expressed in the continuous wars of Louis XIV, and paved the way to the European system based on the balance of power.

The Italian Wars were a series of conflicts fought between 1494 and 1559, mostly in the Italian Peninsula, later expanding into Flanders, the Rhineland and Mediterranean Sea. The primary belligerents were the Valois kings of France, on one side, and their Habsburg opponents in the Holy Roman Empire and Spain on the other. Numerous Italian states participated at different stages, some on both sides, with limited involvement from England, and the Ottoman Empire.

The 1454 Italic League achieved a balance of power in Italy, but disintegrated after the death of its chief architect, Lorenzo de' Medici, in 1492. Combined with the ambition of Ludovico Sforza, its collapse allowed Charles VIII of France to invade Naples in 1494, which drew in Spain and the Holy Roman Empire. Although Charles was forced to withdraw in 1495, ongoing political divisions among the Italian states made them a battleground in the struggle for European domination between France and the Habsburgs.

Otto Eduard Leopold, Prince of Bismarck, Count of Bismarck-Schönhausen, Duke of Lauenburg (/ˈbɪzmɑːrk/; born Otto Eduard Leopold von Bismarck-Schönhausen; 1 April 1815 – 30 July 1898) was a German statesman and diplomat who oversaw the unification of Germany and served as its first chancellor from 1871 to 1890. Bismarck's Realpolitik and firm governance resulted in his being popularly known as the Iron Chancellor (Eiserner Kanzler).

From Junker landowner origins, Bismarck rose rapidly in Prussian politics under King Wilhelm I of Prussia. He served as the Prussian ambassador to Russia and France and in both houses of the Prussian parliament. From 1862 to 1890, he held office as the minister president and foreign minister of Prussia. Under Bismarck's leadership, Prussia provoked three short, decisive wars against Denmark, Austria, and France. After Austria's defeat in 1866, he replaced the German Confederation with the North German Confederation, which aligned the smaller North German states with Prussia while excluding Austria. In 1870, Bismarck secured France's defeat with support from the independent South German states before overseeing the creation of a unified German Empire under Prussian rule. Following Germany's unification, he was given the aristocratic title Prince of Bismarck (Fürst von Bismarck). From 1871 onwards, his balance-of-power approach to diplomacy helped maintain Germany's position in a peaceful Europe. While averse to maritime colonialism, Bismarck acquiesced to elite and popular opinion by acquiring colonies.