Invasion of Yugoslavia in the context of "Balkans campaign (World War II)"

The Tripartite Pact, also known as the Berlin Pact, was an agreement between Germany, Italy, and Japan signed in Berlin on 27 September 1940 by, respectively, Joachim von Ribbentrop, Galeazzo Ciano, and Saburō Kurusu (in that order) and in the presence of Adolf Hitler. It was a defensive military alliance that was eventually joined by Hungary (20 November 1940), Romania (23 November 1940), Slovakia (24 November 1940), Bulgaria (1 March 1941), and Yugoslavia (25 March 1941). Yugoslavia's accession provoked a coup d'état in Belgrade two days later. Germany, Italy, and Hungary responded by invading Yugoslavia. The resulting Italo-German client state, known as the Independent State of Croatia, joined the pact on 15 June 1941.

The Tripartite Pact was, together with the Anti-Comintern Pact and the Pact of Steel, one of a number of agreements between Germany, Japan, Italy, and other countries of the Axis powers governing their relationship.

Croatia, officially the Republic of Croatia, is a country in Central and Southeast Europe, on the coast of the Adriatic Sea. It borders Slovenia to the northwest, Hungary to the northeast, Serbia to the east, Bosnia and Herzegovina and Montenegro to the southeast, and shares a maritime border with Italy to the west. Its capital and largest city, Zagreb, forms one of the country's primary subdivisions, with twenty counties. Other major urban centers include Split, Rijeka and Osijek. The country spans 56,594 square kilometres (21,851 square miles), and has a population of nearly 3.9 million.

The Croats arrived in modern-day Croatia, then part of Roman Illyria, in the late 6th century. In the 7th century, they organized the territory into two duchies. Croatia was first internationally recognized as independent on 7 June 879 during the reign of Duke Branimir. Tomislav became the first king by 925, elevating Croatia to the status of a kingdom. During the succession crisis after the Trpimirović dynasty ended, Croatia entered a personal union with Hungary in 1102. In 1527, faced with Ottoman conquest, the Croatian Parliament elected Ferdinand I of Austria to the Croatian throne. In October 1918, the State of Slovenes, Croats, and Serbs, independent from the Habsburg Empire, was proclaimed in Zagreb, and in December 1918, it merged into the Kingdom of Yugoslavia. Following the Axis invasion of Yugoslavia in April 1941, most of Croatia was incorporated into a Nazi-installed puppet state, the Independent State of Croatia. A resistance movement led to the creation of the Socialist Republic of Croatia, which after the war became a founding member and constituent of the Socialist Federal Republic of Yugoslavia. On 25 June 1991, Croatia declared independence, and the War of Independence was successfully fought over the next four years.

Paul Ludwig Ewald von Kleist (8 August 1881 – 13 November 1954) was a German Generalfeldmarschall (Field Marshal) of the Wehrmacht during World War II. Born into the Prussian noble family von Kleist, Kleist entered the Prussian Army in 1900 and commanded a cavalry squadron during World War I. Kleist joined the Reichswehr of inter-war Germany before being discharged in 1938.

Recalled to active duty at the beginning of World War II, Kleist commanded a motorised corps in the Invasion of Poland. He then became the commander of Panzer Group Kleist (later 1st Panzer Army), the first operational formation of several Panzer corps in the Wehrmacht during the Battle of France, the Battle of Belgium, the Invasion of Yugoslavia and Operation Barbarossa, the invasion of the Soviet Union.

Imperialism, colonialism and irredentism played an important role in the foreign policy of Fascist Italy. These included both ethnic-nationalist irredentist claims and frivolous foreign adventures intended to artificially raise the regime’s prestige. Among the regime's goals were the acquisition of territory considered historically Italian in France (e.g. Nice) and Yugoslavia (e.g. Dalmatia), the expansion of Italy's sphere of influence into the Balkans (e.g. Greece) and the acquisition of more colonies in Africa. The pacification of Libya (1923–32), the invasion of Ethiopia (1935–36), the invasion of Albania (1939), the invasion of France (1940), the invasion of Greece (1940–41) and the invasion of Yugoslavia (1941) were all undertaken in part to add to Italy's national space. According to historian Patrick Bernhard, Fascist Italian imperialism under Benito Mussolini, particularly in Africa, served as a model for the much more famous expansionism of Nazi Germany in Eastern Europe.

On 25 March 1941, Yugoslavia signed the Tripartite Pact with the Axis powers. The agreement was reached after months of negotiations between Germany and Yugoslavia and was signed at the Belvedere in Vienna by Joachim von Ribbentrop, German foreign minister, and Dragiša Cvetković, Yugoslav Prime Minister. Pursuant to the alliance, the parties agreed that the Axis powers would respect Yugoslav sovereignty and territorial integrity, including the Axis refraining from seeking permission to transport troops through Yugoslavia or requesting any military assistance.

Yugoslav accession to the Tripartite Pact (Serbo-Croatian: Тројни пакт / Trojni pakt) was short-lived, however. On 27 March 1941, two days after the agreement had been signed, the Yugoslav government was overthrown when the regency led by Prince Paul was ended and King Peter II fully assumed power. On 6 April 1941, less than two weeks after Yugoslavia had signed onto the Tripartite Pact, the Axis invaded Yugoslavia. By 18 April, the country was conquered and occupied by the Axis powers.

The Independent State of Croatia (Croatian: Nezavisna Država Hrvatska, NDH) was a World War II–era quasi-protectorate of Fascist Italy (1941–1943) and puppet state of Nazi Germany (1941–1945). It was established in parts of occupied Yugoslavia on 10 April 1941, after the invasion by the Axis powers. Its territory consisted mostly of modern-day Croatia and Bosnia and Herzegovina, as well as some parts of modern-day Serbia and Slovenia, but also excluded many Croat-populated areas in Dalmatia (until late 1943), Istria, and Međimurje regions (which today are part of Croatia).

During its entire existence, the NDH was governed as a one-party state by the fascist Ustaše organization. The Ustaše was led by its Poglavnik, Ante Pavelić. The regime targeted Serbs, Jews and Roma as part of a large-scale campaign of genocide, as well as anti-fascist or dissident Croats and Bosnian Muslims. According to Stanley G. Payne, "crimes in the NDH were proportionately surpassed only by Nazi Germany, the Khmer Rouge in Cambodia and several of the extremely genocidal African regimes." In the territory controlled by the NDH, between 1941 and 1945, there existed 22 concentration camps. The largest camp was Jasenovac. Two camps, Jastrebarsko and Sisak, held only children.

Prečani (Serbian Cyrillic: Пречани) was a Serbian blanket term used at the end of the 19th- and early 20th century for ethnic Serb communities located preko ("across") the Drina, Sava and Danube rivers, beyond the western and northern borders of the Principality of Serbia and later Kingdom of Serbia, that is, in Austria-Hungary-held Vojvodina, Bosnia and Herzegovina and Croatia. It was thus used to distinguish Serbs of Serbia, Srbijanci ("Serbians") from those in the Austria-Hungary; it was not applied to the Serbs of Montenegro or those in the Ottoman Empire.

In the Habsburg lands – in Kingdom of Dalmatia, the Serbs established the Serb People's Party, while in the Kingdom of Croatia-Slavonia they established the Serb Independent Party. In 1918 the Prečani Serbs formed a notable political constituency that participated in the founding of the State of Slovenes, Croats and Serbs as well as the joining of Banat, Bačka and Baranja with the Kingdom of Serbia. In the first Yugoslavia, their political party, the Independent Democratic Party was important in national politics. After the invasion of Yugoslavia, they were the main target of the World War II persecution of Serbs.

The League of Communists of Yugoslavia, known until 1952 as the Communist Party of Yugoslavia, was the founding and ruling party of the Socialist Federal Republic of Yugoslavia. It was formed in 1919 as the main communist opposition party in the Kingdom of Serbs, Croats and Slovenes and after its initial successes in the elections, it was proscribed by the royal government and was at times harshly and violently suppressed. It remained an illegal underground group until World War II when, after the invasion of Yugoslavia in 1941, the military arm of the party, the Yugoslav Partisans, became embroiled in a bloody civil war and defeated the Axis powers and their local auxiliaries. After the liberation from foreign occupation in 1945, the party consolidated its power and established a one-party state, which existed in that form of government until 1990, a year prior to the start of the Yugoslav Wars and breakup of Yugoslavia.

Led by Josip Broz Tito from 1937 to 1980, it was the first communist party in power to defy the Soviet hegemony in the Eastern Bloc and thus was expelled from the Cominform in 1948 in what is known as the Tito–Stalin split. After internal purges of pro-Soviet members, the party renamed itself the League of Communists in 1952 and adopted the politics of workers' self-management and an independent path to achieving socialism, known as Titoism.