This was a Yugoslav operation against the Croat forces in the Bosnia and Herzegovina areas of Yugoslavia as the last land battle of World War II on the European continent (19 April/25 May 1945).
In November 1944 the so-called Independent State of Croatia, a German puppet, reorganised its armed forces to combine all Ustaše units and the Croat army into 18 divisions, comprising 13 infantry, two mountain and two assault divisions plus one replacement division, each with its own organic artillery and other support units. There were also several armoured units. From early 1945 the divisions were allocated to various German corps, and by March 1945 the Croat formations were holding the southern front in German-occupied Yugoslavia.
By the spring of 1945 the German forces and their collaborationist allies were in full retreat from the Yugoslav army. Early in April the Yugoslav 3rd Army, under the command of Lieutenant General Kosta Nađ, fanned out through the Podravina region centred on the valley of the Drava river, reaching a point to the north of Zagreb, and crossed the previous Austro-Yugoslav border in the Dravograd sector. The 3rd Army thus closed the ring around the Axis forces when its leading motorised detachments linked with elements of the 4th Army in Carinthia. This action prevented Generaloberst Alexander Löhr’s Heeresgruppe 'E' from escaping to the north-west across the Drava river. Completely surrounded, Löhr was forced to sign the unconditional surrender of the forces under his command (General Hartwig von Ludwiger’s XXI Gebirgskorps and General Hellmuth Felmy’s XXXIV Corps) at Topolsica, near Velenje in Slovenia, on 9 May. Notwithstanding the terms of the surrender, some of Löhr’s troops, along with collaborationist forces including Croat armed forces, the Slovene Home Guard, the Montenegrin People’s Army (former Četniks), and elements of other factions, continued to resist the Yugoslav forces as they sought to fight their way to the west and seek the protection of the British forces at Klagenfurt in Austria.
The battle ended 17 days after the formal termination of hostilities in Europe, and pitted a Yugoslav army forces commanded by Milos Zekić against a Croat army force commanded by Petar Rajkovačić-Baja. Fought in the Bosnian town of Odzak, the battle was a Pyrrhic victory for the Yugoslavs, but all information about it was suppressed by the Yugoslav government until a newspaper reported the battle in 1975.
Despite the fact that a January 1945 amnesty offered by Marshal Josip Broz Tito, the Yugoslav leader, had expired, some of the Croat troops nonetheless defected to the partisans in the hope of joining the winning side, and many others disappeared to return home. Most of these had tried to withdraw with the Germans, however, and many of them found themselves cut off by rapid Yugoslav advances. Of these last, those who did not surrender sought to conceal themselves in forest and mountain regions.
In May 1945 the Croat armed forces began to retreat toward Austria after the decision of Ante Pavelić, the ruler of the rapidly disintegrating Independent State of Croatia, that there would be no defence of Zagreb, the Croat capital. But a force sometimes estimated as up to 11,000 troops under the command of the brothers Ivan and Petar Rajkovačić-Baja decided that it would in fact defend Zagreb. On 19 April this force took the town of Odzak and 24 nearby villages, and established a stronghold in the area where the Bosna river enters the Sava river. Thus the Croats dug in around Odzak, Vlaska Mala and Prud. It is probable that this Croat force’s actual strength was between 2,500 and 3,500 men of the local Ustase (6th Ustase Battalion and remnants of the 12th Ustase Brigade) and militia units together with the remnants of 12th and 15th Divisions supported by eight mortars. The two most important commanders were Petar Rajkovačić-Baja and Ivo Čilucić, and their forces were centred on the village of Vlacka Mala, which included a two-storey bunker dominating the surrounding area in the triangular area bounded by Odzak, Potočani and Svilaj. The Croat positions were linked by trenches reinforced with earth and concrete bunkers, together with fortified buildings, the whole surrounded by barbed wire.
Thus the remaining strength of the Croat forces now sought to hold all that was left of their nation, which was a narrow area between the Bosna and Sava rivers that included Novigrad, Donji Brezik, Vlaska Mala, Odzak and Mrka Ada. The area also also held large numbers of Bosnian Moslem refugees from Kladanj, Plehana, Tepče, Sive, Gračanica and nearby populated places.
The headquarters of the III Partisan Corps, comprising the 27th, 28th and 53rd Divisions, ordered an immediate attack on the Croat stronghold. The Yugoslav strength is also uncertain, for in these closing weeks of the war constant combat has depleted every unit and there were few replacements, if any at all. Thus the average brigade strength was between 1,000 and 1,500 men, and with three or four brigades involved this gave Tito’s force a strength of only 4,000 to 5,000 men with limited artillery support and no armour.
The 'Vlaska Mala' offensive which the Yugoslav army now launched was fought in two phases on 19/28 April and 3/25 May. The offensive was undertaken by the Yugoslav 25th 'Serb' Division and the 16th Moslem Brigade of the 27th Division. After limited initial successes, the 25th Division was checked in front of Vlaska Mala after killing 74, wounding 126 and capturing 2,178 (eight Ustase, 1,275 Croat and 895 Četnik personnel) in the villages of Jakec and Pečnik, and in Odzak. The 25th Division’s subsequent attacks were repulsed, after which the division was pulled out to join the 'Una' Divisional Group.
The 16th Brigade now attacked the exposed Odzak sector on its own, but after early success was driven back by a Ustase group which counterattacked and retook Odzak and attempted to capture the ferry crossing near Modriča but was stopped just short of the Bosna and pushed back.
Between 29 April and 3 May the two sides regrouped. The Ustase group did not avail itself of the opportunity to escape to the west, instead deciding to remain in its fortified area. Over the same period the 27th Division brought up its 19th 'Birač' and 20th 'Romanija' Brigades to support the 16th Brigade. Limited night attacks on 1/2 and 2/3 May by newly arrived units pushed the Ustase out of the village of Potočane by 3 May. Potočane dominated the surrounding area, and the 25th Division decided to launch major assault during the evening of May 5.
Lacking the strength to deliver simultaneous attacks on both the Ustase group at Odzak and General Draza Mihailović's Četnik group, the III Corps left covering force near Vlaska Mala while most of the 27th and 53rd Divisions eliminated Četnik group. Between 9 and 22 May the Yugoslavs prepared a major assault on Vlaska Mala, and from 15 May seven ex-German and ex-Italian aircraft of the Mixed Squadron and Mostar Squadron carried out daily attacks, supplemented from 21 May by larger-scale attacks by 15 Ilyushin Il-2 attack aircraft of the 421st Assault Regiment from the airfield at Laćarak. No armour could be used as the bridges over the Sava river had been destroyed.
Attacks on 22 and 23 May failed to break the Croat defences, even though pointblank artillery fire was used to destroy bunkers. At 23.000 on 24 May Odzak was taken by the 19th 'Birač' and 20th 'Romanija' Brigades. The final assault on Vlaska Mala was launched at 04.00 on 25 May, but ran into a break-out attempt by the defenders through positions of the 16th Brigade. By morning the Ustase group had been pushed back into the open, where it was destroyed. Meanwhile Vlaska Mala was captured by the 14th 'Central Bosnia' Brigade. Both Rajkovačić and Čilucić managed to escape to the Vučjak mountain area. The 25th and 27th Divisions suffered something in the order of 1,060 casualties, while the Ustase lost 881 men killed, 104 wounded and 572 captured, together with one mortar, 44 machine guns and 584 rifles.
It is worth noting that the men of the first group which failed to break out of the encirclement were taken into captivity. The men of the other group succeeded in entering Lipa and Plandiste. In Odzak, the Yugoslav troops arrested all males aged 15 or more, but not infrequently just killed boys of about 10. There followed mass executions, though some men escaped and took refuge in the local forests, from which they undertook guerrilla raids until the spring of 1947, when the last man was killed in Lipa.