The Independent State of Croatia (Nezavisna Država Hrvatska, NDH) was a puppet-state of Fascist Italy and Nazi Germany.

Geography

History
Following the attack of the Axis powers on the Kingdom of Yugoslavia in 1941, and the quick defeat of the Yugoslav army (Jugoslovenska vojska), the whole country was occupied by Axis forces. Hitler and Mussolini installed the Croatian Ustaše, who had long sought Croatian independence, forming the Independent State of Croatia (NDH - Nezavisna Država Hrvatska).
The establishment of NDH was proclaimed on April 10, 1941 by Slavko Kvaternik, deputy leader of the Ustaše. Ante Pavelić came to power as leader (Poglavnik) of the Croatian puppet state. Pavelić took power with Mussolini and Hitler's blessing. The crown of this puppet state was handed to Aymon, Duke of Spoleto, of the house of Savoy. The Duke never set foot in Zagreb nor was really interested in his "kingdom".
This article is part of the series on the History of Croatia

Establishment of NDH
The Ustaše initially did not have a capable army or administration necessary to control all of this territory: the movement had fewer than 12,000 members when the war broke out, and not nearly all of them were deployed during the invasion. Therefore the territory was controlled by the Germans and the Italians:
NDH would eventually build up its own army, divided into two main groups:
Together they mustered about 110,000 troops by the end of 1942, and about 130,000 in 1943 and were initially equipped mainly with captured Royal Yugoslav Army weapons and equipment, as well as some ex-Italian and ex-Polish light armoured vehicles. On the other hand, the NDH had no navy, owing to the terms of the Rome Agreement with Italy. The air force was modest as well, initially consisting of captured Royal Yugoslav aircraft (7 operational fighters and 20 bombers, as well some 150 auxiliary and training aircraft), but also supplemented by further German, Italian and French fighters and bombers right up until March 1945.

the northeastern half of NDH territory was under the so-called German zone of influence, with the Wehrmacht making its presence
the southwestern half was controlled by the Italian Fascist army. After the capitulation of Italy in 1943, NDH acquired northern Dalmatia (Split and Šibenik)
Ustaše proper constituted the elite militia (Croatian Ustaška vojnica)
Home Guard or Domobrani was the much larger regular army Initial period
The state of permanent terror, mass killing, raping women and looting properties of their victims in the Independent State of Croatia forced, primarily, the Serbs to rebel. According to the Glaise von Horstenau Appointed general Horstenau wrote in his report: »Ustashe movement is, due to the mistakes and atrocities they have made, and the corruption, so compromised that the government executive branch (the homeguard and the police) shall be separated from the government - even for the price of breaking any possible connection with the government ..."

Uprising
In August 1944, there was an attempt by foreign Minister in NDH government Mladen Lorković and Minister of War Ante Vokić to execute a coup d'etat against Ante Pavelić. The coup (called Lorković-Vokić coup) failed and its conspirators were executed.
The NDH army withdrew towards Zagreb with German and Cossak troops by early 1945, and continued fighting for a week after the German surrender on May 9th, 1945. They were soon overpowered and the Independent State of Croatia (NDH) effectively ceased to exist in May 1945, near the end of the war. The advance of Tito's partisan forces, joined by the Soviet Red Army, caused mass retreat of the Ustaše towards Austria.
In May 1945, a large column composed of anti-communists, Ustaša followers, NDH Army troops and civilians retreated from the partisan forces, heading northwest towards Italy and Austria. Ante Pavelić detached from the group and fled to Austria, Italy and finally Argentina. The rest of the group, consisting of over 150,000 soldiers (including Cossak troops) and civilians negotiated passage with the British forces on the Austrian side of the Austrian-Slovenian border. The British Army then turned over a number of them to the partisan forces. Some of them were court-martialled and executed on spot.
The end of the war resulted in the establishment of the Socialist Federal Republic of Yugoslavia, with the constitution of 1946 officially making Croatia and Bosnia and Herzegovina one of six constituent republics in the new state.

End of the war
According to the data presented by former Austro-Hungarian officer Hefner, the population of the Independent State of Croatia numbered 6,042,000 people (data from 1941-04-23), including:
According to another source, the Independent State of Croatia had a population of 6,300,000 and was ethnically diverse - the relative majority was held by Croats, but as Bosnian Muslims were counted as Croats, Croats held absolute majority according to Ustashe ideology, while over 33% (2,100,000) of the populace were Serbs (of whom most were Orthodox Christian); around 50% of the population were Catholics (Germans and Hungarians, aside from Croats). 750,000 inhabitants of the independent state of Croatia were Muslims. There was a significant minority of 30,000 Jews living mostly in Sarajevo, Zagreb and Osijek. Authorities soon disbanded the Serbian Orthodox Church on their territory and established Croatian Orthodox Church whose patriarch was Germogen, an exiled Russian.

Croats = 3,069,000 (50.78%)
Serbs = 1,847,000 (30.65%)
Muslims = 717,000 (11.86%)
others = 410,000 (6.80%), of whom:

• Germans = 150,000
  Hungarians = 75,000
  Slovaks and Czechs= 65,000
  Jews = 40,000
  Slovenians = 37,000
  Italians = 5,000 Population
  A large number of people were displaced due to internal fighting within the republic. The NDH also had to accept more than 200,000 Slovenian refugees which were forcefully evicted from their homes as part of the German plan of annexing parts of the Slovenian territories. As part of this deal, the Ustaše were to deport 200,000 Serbs from Croatia military; however, only 182,000 were deported due to the German high commander Bader stopping this mass transport of people because of the Chetniks and partisan uprising in Serbia. Because of this, 25,000 Slovenian refugees ended in Serbia.
  
  Displacement of people
  The previously important civic factors, the Croatian Peasant Party (HSS) and the Catholic Church, were reasonably uninvolved in the creation and maintenance of the Independent State of Croatia. All who opposed and/or threatened the Ustaše were eventually outlawed.
  The Ustaše government tried to convene a Croatian Parliament (as Hrvatski državni Sabor NDH) in 1942, with a manually selected list of deputies, but after three short sessions, parliament ceased operation by the end of the same year.
  The HSS was banned on June 11, 1941 in an attempt of the Ustaše to take their place as the primary representative of the Croatian peasantry. Vladko Maček was sent to Jasenovac concentration camp, but later released to serve a house arrest sentence due to his popularity among the people. Maček was later again called upon by the foreigners to take a stand and counteract the Pavelić government, but he refused.
  The Catholic Church participated in religious conversions at first, but eventually the main branches of the Church stopped doing so, as it became obvious that these conversions were merely a lesser form of punishment for the undesirable population. Nevertheless, a number of priests joined the Ustaše ranks.