Interwar period in the context of "Angled flight deck"

The causes of World War II have been given considerable attention by historians. The immediate precipitating event was the invasion of Poland by Nazi Germany on September 1, 1939, and the subsequent declarations of war on Germany made by Britain and France, but many other prior events have been suggested as ultimate causes. Primary themes in historical analysis of the war's origins include the political takeover of Germany in 1933 by Adolf Hitler and the Nazi Party; Japanese militarism against China, which led to the Japanese invasion of Manchuria and the Second Sino-Japanese War; Italian aggression against Ethiopia, which led to the Second Italo-Ethiopian War; or military uprising in Spain, which led to the Spanish Civil War.

During the interwar period, deep anger arose in the Weimar Republic over the conditions of the 1919 Treaty of Versailles, which punished Germany for its role in World War I with heavy financial reparations and severe limitations on its military that were intended to prevent it from becoming a military power again. The demilitarisation of the Rhineland, the prohibition of German unification with Austria, and the loss of its overseas colonies as well as some 12% of the pre-war land area and population of the metropole all provoked strong currents of revanchism in German politics.

The Spanish Civil War (Spanish: guerra civil española) was fought from 1936 to 1939 between the Republicans and the Nationalists. Republicans were loyal to the left-leaning Popular Front government of the Second Spanish Republic and included socialists, anarchists, communists, and separatists. The opposing Nationalists who established the Spanish State were an alliance of fascist Falangists, monarchists, conservatives, and traditionalists supported by Nazi Germany and Fascist Italy and led by a military junta among whom General Francisco Franco quickly achieved a preponderant role. Due to the international political climate at the time, the war was variously viewed as class struggle, a religious struggle, or a struggle between dictatorship and republican democracy, between revolution and counterrevolution, or between fascism and communism. The Nationalists won the war, which ended in early 1939, and ruled Spain until Franco's death in November 1975.

The war began after the partial failure of the coup d'état of July 1936 against the Popular Front government by a group of generals of the Spanish Republican Armed Forces. The Nationalist faction consisted of right-wing groups, including Christian traditionalist party CEDA, monarchists, including both the opposing Alfonsists and the religious conservative Carlists, and the Falange Española de las JONS, a fascist political party. However, rebelling units in almost all important cities did not gain control, leaving Spain militarily and politically divided. The rebellion was countered with the help of arming left-wing social movements and parties and formation of militias, what led to rapid socioeconomic and political transformation in the Republican zone, referred to as the Spanish Revolution. The Nationalist forces received munitions, soldiers, and air support from Fascist Italy and Nazi Germany while the Republican side received support from the Soviet Union and Mexico. Other countries, such as the United Kingdom, France, and the United States, continued to recognise the Republican government but followed an official policy of non-intervention. Despite this policy, tens of thousands of citizens from non-interventionist countries directly participated in the conflict, mostly in the pro-Republican International Brigades.

A post-war or postwar period is the interval immediately following the end of a war. The term usually refers to a varying period of time after World War II, which ended in 1945. A post-war period can become an interwar period or interbellum, when a war between the same parties resumes at a later date (such as the period between World War I and World War II). By contrast, a post-war period marks the cessation of armed conflict entirely.

Bosnia and Herzegovina, often referred to as Bosnia-Herzegovina or short as Bosnia, is a country in Southeast Europe. Situated on the Balkan Peninsula, it borders Serbia to the east, Montenegro to the southeast, and Croatia to the north and southwest, with a 20-kilometre-long (12-mile) coast on the Adriatic Sea in the south. Bosnia has a moderate continental climate with hot summers and cold, snowy winters. Its geography is largely mountainous, particularly in the central and eastern regions, which are dominated by the Dinaric Alps. Herzegovina, the smaller, southern region, has a Mediterranean climate and is mostly mountainous. Sarajevo is the capital and the largest city.

The area has been inhabited since at least the Upper Palaeolithic, with permanent human settlement traced to the Neolithic cultures of Butmir, Kakanj, and Vučedol. After the arrival of the first Indo-Europeans, the area was populated by several Illyrian and Celtic civilisations. Most of modern Bosnia was incorporated into the Roman province of Dalmatia by the mid-first century BCE. The ancestors of the modern South Slavic peoples arrived between the sixth and ninth centuries. In the 12th century, the Banate of Bosnia was established as the first independent Bosnian polity. It gradually evolved and expanded into the Kingdom of Bosnia, which became the most powerful state in the western Balkans by the 14th century. The Ottoman Empire annexed the region in 1463 and introduced Islam. From the late 19th century until World War I, the country was annexed into the Austro-Hungarian monarchy. In the interwar period, Bosnia and Herzegovina was part of the Kingdom of Yugoslavia. After World War II, it was granted full republic status in the newly formed Socialist Federal Republic of Yugoslavia. In 1992, following the breakup of Yugoslavia, the republic proclaimed independence. This was followed by the Bosnian War, which lasted until late 1995 and ended with the signing of the Dayton Agreement.

Yugoslavism, Yugoslavdom, or Yugoslav nationalism is an ideology supporting the notion that the South Slavs, namely the Bosniaks, Bulgarians, Croats, Macedonians, Montenegrins, Serbs, and Slovenes, belong to a single Yugoslav nation separated by diverging historical circumstances, forms of speech, and religious divides. During the interwar period, Yugoslavism became predominant in, and then the official ideology of, the Kingdom of Yugoslavia. There were two major forms of Yugoslavism in the period, the first of which is the regime-favoured integral Yugoslavism, promoting unitarism, centralisation, and unification of the country's ethnic groups into a single Yugoslav nation, by coercion if necessary. The approach was also applied to languages spoken in the Kingdom. The main alternative was federalist Yugoslavism, which advocated the autonomy of the historical lands in the form of a federation and gradual unification without outside pressure. Both agreed on the concept of National Oneness developed as an expression of the strategic alliance of South Slavs in Austria-Hungary in the early 20th century. The concept was meant as a notion that the South Slavs belong to a single "race", were of "one blood", and had shared language. It was considered neutral regarding the choice of centralism or federalism.

The Yugoslavist idea has roots in the 1830s Illyrian movement in Habsburg Croatia, where a group of intellectuals saw the unity of South Slavs within the Austrian Empire or outside of it as a protection against Germanisation and Magyarisation. Cooperative talks began with Serbian politicians and working to standardise Serbo-Croatian as a common language with orthographer Vuk Karadžić, with limited success. Following the Austro-Hungarian Compromise of 1867, the concept was rivalled by Trialism. Control of the Balkans by the Ottoman Empire and Austria-Hungary prevented practical implementation of Yugoslavist ideas until the Ottomans were pushed out of the Balkans in the 1912 First Balkan War and Austria-Hungary disintegrated in the final days of the First World War. During the war, preparations for unification began in the form of the Niš Declaration of Serbian war aims, the establishment of the Yugoslav Committee to represent South Slavs living in Austria-Hungary, and the adoption of the Corfu Declaration on principles of unification. The short-lived State of Slovenes, Croats and Serbs was proclaimed in the South Slavic lands formerly ruled by the Habsburgs at the end of the First World War. Its leadership primarily wanted unification with Serbia on a federal basis, while Serbia preferred a centralised state.

Greater Romania (Romanian: România Mare) is the Kingdom of Romania during the interwar period, within its borders achieved after the Great Union; or the related pan-nationalist ideal of a nation state which would incorporate all Romanian-speakers.

In 1920, after the incorporation of Transylvania, Bukovina, Bessarabia and parts of Banat, Crișana, and Maramureș, the Romanian state reached its largest peacetime geographical extent (295,049 km). Today, the concept serves as a guiding principle for the unification of Moldova and Romania.

Estonia, officially the Republic of Estonia, is a country in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the Baltic Sea across from Sweden, to the south by Latvia, and to the east by Russia. The territory of Estonia consists of the mainland, the larger islands of Saaremaa and Hiiumaa, and over 2,300 other islands and islets on the east coast of the Baltic Sea. Its capital Tallinn and Tartu are the two largest urban areas. The Estonian language, of the Finnic family, is the official language and the first language of the majority of its population of nearly 1.4 million. Estonia is one of the least populous members of the European Union and NATO.

Present-day Estonia has been inhabited since at least 9,000 BC. The medieval indigenous population of Estonia was one of the last pagan civilisations in Europe to adopt Christianity following the Northern Crusades in the 13th century. After centuries of successive rule by the Teutonic Order, Denmark, Sweden, and the Russian Empire, a distinct Estonian national identity began to emerge in the mid-19th century. This culminated in the 1918 Estonian Declaration of Independence from the then-warring Russian and German empires. Democratic throughout most of the interwar period, Estonia declared neutrality at the outbreak of World War II, but the country was repeatedly invaded and occupied, and ultimately annexed into the USSR. Throughout the de facto Soviet occupation, from World War II until 1991, Estonia's de jure state continuity was preserved by diplomatic representatives and the government-in-exile. Following the 1988–90 "Singing Revolution" against Soviet rule, full independence was restored on 20 August 1991.

The Frankfurt School is a school of thought in sociology and critical theory. It is associated with the Institute for Social Research founded in 1923 at the University of Frankfurt am Main (today known as Goethe University Frankfurt). Formed during the Weimar Republic during the European interwar period, the first generation of the Frankfurt School was composed of intellectuals, academics, and political dissidents dissatisfied with the socio-economic systems of the 1930s: namely, capitalism, fascism, and communism. Significant figures associated with the school include Max Horkheimer, Theodor Adorno, Walter Benjamin, Erich Fromm, Wilhelm Reich, Herbert Marcuse, and Jürgen Habermas.

The Frankfurt theorists proposed that existing social theory was unable to explain the turbulent political factionalism and reactionary politics, such as Nazism, of 20th-century liberal capitalist societies. Also critical of Marxism–Leninism as a philosophically inflexible system of social organization, the School's critical-theory research sought alternative paths to social development.

Neo-Byzantine architecture (also referred to as Byzantine Revival) was a revival movement, most frequently seen in religious, institutional and public buildings. It incorporates elements of the Byzantine style associated with Eastern and Orthodox Christian architecture dating from the 5th through 11th centuries, notably that of Constantinople (present-day Istanbul) and the Exarchate of Ravenna.

Neo-Byzantine architecture emerged in the 1840s in Western Europe and peaked in the last quarter of the 19th century with the Sacré-Coeur Basilica in Paris, and with monumental works in the Russian Empire, and later Bulgaria. The Neo-Byzantine school was active in Yugoslavia in the interwar period.

The Sudetenland (/suːˈdeɪtənlænd/ soo-DAY-tən-land, German: [zuˈdeːtn̩ˌlant]; Czech and Slovak: Sudety) is a German name for the northern, southern, and western areas of former Czechoslovakia which were inhabited primarily by Sudeten Germans. These German speakers had predominated in the border districts of Bohemia, Moravia, and Czech Silesia since the Middle Ages.

The word "Sudetenland" did not come into being until the early part of the 20th century and did not come to prominence until almost two decades into the century, after World War I, when Austria-Hungary disintegrated and the Sudeten Germans found themselves living in the new country of Czechoslovakia. The Sudeten crisis of 1938 was provoked by the Pan-Germanist demands of Nazi Germany that the Sudetenland be annexed to Germany, which happened after the later Munich Agreement. Part of the borderland was invaded and annexed by Poland. Afterwards, the formerly unrecognized Sudetenland became an administrative division of Germany. When Czechoslovakia was reconstituted after World War II, the Sudeten Germans were expelled and the region today is inhabited almost exclusively by Czech speakers.