April 1941

The Communist movement under the leadership of Josip Broz Tito, a Croat appointed by the Communist International, decided for the armed resistance against the occupying forces and their domestic allies. Following such a course, the Communist leadership recognized the possibility for seizure of power in the country.

1941

Ustashe massacres of Serbian population on the territories of Croatia and Bosnia and Hercegovina,as well as Chetnik massacres of Croatian and Bosnian Muslim peoples.
The mass rebellion of Tito's Communist Army in Serbia and Montenegro was broken down till the end of the year by the powerful German and Italian offensive with the help of Serbian Fascists and Chetniks. The Communist Partisans were cut down from about 50,000 soldiers to 4,500 fighters and expelled out of Serbia. The war continued with the greatest intensity on the territories of Croatia and Bosnia and Hercegovina.

1942  - 1943

Crucial period for creating Bosnia as well as whole Yugoslavia in the next half a century.

On the military level maximal concentration of the opposing forces appeared: along with about 160,000 German and 350,000 Italian, armed power of NDH achieved the manpower of over 160,000, and Chetniks of Draza Mihailovic counted ca 80,000 soldiers. The Communist Army, numbering 150,000 Partisans,leads exhausting guerilla warfare, retreating before the enemy's offensives and hardly breaking out of the enemy surround.

While the armed forces of NDH consisted exclusively of Croats and Bosnian Muslims, and Chetnik forces of Serbs, Tito's Communist Army was multiethnic, being a conglomerate of various nations. It counted about 44% Serbs, 30% Croats, 10% Slovenes, as well as Montenegrins and Muslims. From the Partisans brigades, great majority was Croatian and Bosnian: from 96 brigades 38 were Croatian, 23 Bosnian and Hercegovinian and 17 Slovenian, which shows that the war was fought with the greatest intensity on the territory of NDH, while Serbia and Montenegro were mostly pacified and under the Chetnik control.

Important battles were led from January ( so called the Battle on Neretva or the 4th Offensive) and from May ( so called the Battle on Sutjeska or the 5th Offensive) in 1943 - both having the aim to surround and destroy Tito's army and both fought nearly completely on the territory of NDH. The most important result of the 4th Offensive was the survival of Partisan movement, which succeeded to rout the Chetnik main forces and politically marginalize them. In that operations one third of Partisans was killed-50% of them Croats, but Chetnik royalist movement was eliminated as the real political option. In the 5th Offensive,which lasted during autumn, the Communist Army hardly, with heavy losses, broke the German-Italian encirclement. But, having preserved the Partisan core, Tito succeeded to capitalize on the collapse of Fascist Italy - except weapons, his army quickly grew by the mass inflow of new soldiers, mostly Croats and Slovenes, so that till the end of 1943 it counted 300,000 fighters.

On the political level the most important was the session of the supreme partisan political body - AVNOJ - on the 29th November 1943 in Bosnian town Jajce.
Decisions which sealed the destiny of Kingdom of Yugoslavia were as follows:
- the supreme partisan political body AVNOJ becomes the main legislative council and the highest representative of sovereignity of all Yugoslav nations
- foundation of the provisional government
- all the rights of emigre Yugoslav government are taken away
- the return of the king Petar II Karadjordjevic to Yugoslavia is forbidden
- new Yugoslavia will be federal state union of nations having equal rights
- Tito is assigned the title Marshal of Yugoslavia
- the state commission is founded for investigation of the war crimes of the occupying forces and their collaborators.

1944

On the island Vis the agreement was signed between the Marshal Tito and the former Ban of the Croatian Banovina Ivan Subasic, who became the president of the Yugoslav emigre government. Subasic engaged himself that his government would recognize AVNOJ and to call in people to join the anti-fascist movement. Thereby, the international community and the British government definitely recognized legitimacy and the rule of Tito's Army(NOVJ) and its institutions.

1945  - middle of the May

Near the Austrian frontier, in Bleiburg, the massive brutalization of Croats had begun, perpetrated by the Partisan Army with numerous amnested Chetniks from Serbia enlisted. In the last battles and in "death marches" about 50,000 Croats, members of the NDH armed forces, their families and civilians, were killed or died. Many of them fell into the Partisan captivity suffering on the long "Way of the Cross". But, these are the facts based on the demographic estimates of Croatian scientist Zerjavic and Serbian Kocovic.
According to these analyses which give very similiar results, Yugoslavia lost about a million people in the World War II, out of them about 500,000 Serbs, 200,000 Croats and 90,000 Bosnian Muslims. Bosnia and Hercegovina suffered the following losses: 164,000 Serbs, 64,000 Croats, 75,000 Muslims and 9,000 Jews.
But, more recent exhumations which were done on the places of execution in Slovenia after the fall of Communism have brought some doubts about this statistics: against 50,000 Croats killed by the Communists on the whole territory from Austria to Macedonia, the Slovenian Commission for War Crimes identified about 190,000 people killed in Partisan massacres in 1945/1946. As according to the discovery of the Commission, about 10,000 belonged to the members of Slovenian Home Defence Guards, and 180,000 to Croatian soldiers and civilians ,this asks new questions -not bringing into doubt the status of Marshal Josip Broz Tito as the greatest war criminal on the territory of the former Yugoslavia.