'Südost-Kroatien' was a German, Italian and Croat pair of operations ('Südost-Kroatien I' and 'Südost-Kroatien II') against the partisan forces of Josip Broz Tito in the puppet state of Croatia in Axis-occupied Yugoslavia (January/February 1942).
Undertaken between 15 and 23 January at the behest of General Paul Bader, the Militärbefehlshaber in Serbien, 'Südost-Kroatien I' had as its objective the destruction of the partisan 1st Proletarian Brigade, 'Romanija' Partisan Detachment, 'Birčanski' Partisan Detachment and 'Zvijezda' Partisan Detachment, supported by a few Četnik units, in the Romanija Gora (mountain region) bordered by Sarajevo, Visegrad, Zvornik, Tuzla and Vares.
The Axis offensive was entrusted to a force of 20,000 to 25,000 men provided by the Germans (Generalmajor Paul Hoffmannss 342nd Division, elements of Generalleutnant Friedrich Stahlss 714th Division, Generalleutnant Johann Fortnerss 718th Division and a reinforced company of the 202nd Panzerregiment with 19 tanks), the Italian (3o Reggimento alpino of Generale di Divisione Giovanni Maccario’s 1a Divisione alpina 'Taurinense'), and the Croats (2 and 4/3rd Regiment, 6th and 7th Artillery Groups, reinforced 2/8th Regiment, reinforced 1 and 2/15th Regiment, 1st Battery/9th Artillery Group, 2nd Battery/11th Artillery Group, 1 and 2/13th Regiment, 3rd Company/3rd Engineer Battalion, Mountain Gun Battery of the Military Frontier Troops, three battalions of the Ustase 'Black Legion' and one battalion of the 'Hadziefendić' Moslem Militia).
The 718th Division and attached Croat units were deployed in the area between Sarajevo and Tuzla with orders to advance toward the 342nd Division and other German and Croat units positioned along the Drina river between Zvornik and Visegrad and thereby encircle and destroy the partisans in a pincer movement. During the next nine days, these forces pushed toward each other through deep snow and mountainous terrain, and met only limited partisan resistance. The area was successfully cleared and most partisan-held towns and villages were retaken, but most of the partisans managed to avoid a frontal engagement and slipped through gaps in the tightening Axis net.
Undertaken between 28 January and 2 February, 'Südost-Kroatien II' was the logical successor to 'Südost-Kroatien I', which had isolated a large force of partisans and Četniks in the Ozren mountain region to the east of Doboj and Maglaj. Otherwise known as 'Ozren', 'Südost-Kroatien II' was therefore aimed at the destruction of the 'Ozren' Partisan Detachment (estimated at 1,200 men in five battalions), and was a German and Croat undertaking using about 18,000 men.
The German contribution was the 697th Regiment of the 342nd Division, 738th Infanterieregiment and 750th Infanterieregiment of the 718th Division, and five batteries of mountain guns, and the Croat contribution comprised the headquarters and staffs of Pukovnik Emil Radl’s 3rd Division and Pukovnik Artur Gustović's 4th Division, 4 and 5/1st Regiment, 1 and 3/5th Regiment, elements of the 3rd and 4th Artillery Groups, two battalions of the 4th Division, 3rd 'Legionnaire' Battalion, half of a battalion of the Ustase 'Black Legion', and one battalion of the 'Hadziefendić' Moslem Militia.
A northern combat group of Croat forces was assembled along the line linking Dobij and Maglaj, a second group to the north-east of Tuzla and a southern group, made up mainly of Ustase, around the village of Usora to the south-east of Maglaj. The German troops were deployed as a blocking force along the line between Zavidovići and Lukavac.
The operation started on the morning of 28 January with an artillery barrage, and took the partisan detachment by complete surprise. While advancing on 29 January, the men of the 'Black Legion' burned down several Serb villages in the Krivaja river valley. By 30 January, the partisans and Četniks had been driven out of their mountain positions and herded to the south-west against the German blocking group, by which they were either killed or captured. 'Südost-Kroatien I' and 'Südost-Kroatien II' cost the partisans and, to a considerably more limited extent, the Četniks 521 dead, an unknown number of wounded, and 1,331 taken prisoner. The combined German and Croat force lost 25 dead, 131 wounded and 300 incapacitated by frostbite.
Although their losses were relatively high, the partisans were mostly able to get away, either by moving south into the Italian zone of occupation or by hiding in the mountains.