'Jajce' (i) was the German-led pair of components in the Axis multi-phase 'Dinara' plan in occupied Yugoslavia to regain the parts of central Bosnia which had been liberated by the partisan forces of Josip Broz Tito (28 September/7 October and 21/31 October 1942).
The Axis forces committed in 'Jajce I' were Generalleutnant Friedrich Stahl’s 714th Division, Generalleutnant Johann Fortner’s 718th Division, the Bataillon 'Ludwig von Baden', the 21st Ustase Battalion, elements of General Djuro Iser’s Croat II Domobran Corps and General Mihajlo Lukić's III Domobran Corps, five detachments of the general staff of the Bosnian Četnik movement, and the Combat Group 'Sanski Most' comprising the 3/741st Regiment and 2/10th Domobran Regiment.
Starting on 28 September, 'Jajce I' was designed as a concentric attack from the areas of Sanski Most and Banja Luka on the one hand and Donji Vakuf and Travnik on the other, and by 6 October had regained control of Ključ, Mrkonjić-Grad and Jajce. Within this overall picture, the Combat Group 'Sanski Most' (reinforced by armour, artillery and local Četnik elements) fought for two days against elements of the 6th 'Krajina' Partisan Detachment to take Ključ on 29 September. On 2 October, employing an encirclement manoeuvre across Lisina mountain, Oberstleutnant von Wedel’s Kampfgruppe 'Wedel' (721st Regiment) drove back the partisan 2nd Proletarian Brigade toward the village of Jezero and captured Mrkonjić-Grad.
Despite a partisan strength of six brigades and two independent detachments in the Bosnian Krajina sector, poor communications meant that the partisans were unable to offer more than a token resistance, but nonetheless managed to withdraw their units in the face of determined assaults by a stronger opponent, and on 6 October launched a counterattack with five brigades and parts of two detachments in the area of the upper Sana river.
In the course of three days of major fighting, the partisan forces retook Ključ and destroyed several Axis garrisons between Sitinica and Vrhpolje, but their advance toward Sanski Most was halted in its tracks by the regimental-sized Kampfgruppe 'Wedel' from Sitinica. On 7 October the 1st Proletarian Brigade and parts of 6th 'Krajina' Detachment broke the reinforced 2/10th Domobran Regiment and captured Ključ.
On 21 October the Germans launched 'Jajce II', an 11-day undertaking with the goal of destroying all the partisan units in Janj and Pljeva. The Axis forces committed in the 'Jajce II' undertaking were the 718th Division, a Croat contingent (nine infantry battalions, four artillery battalions and one armoured battalion), and the German-Croat-Četnik Kampfgruppe 'Tomas' of two battalions. Above the village of Jezero, the German regimental-sized Kampfgruppe 'Susin' of the 718th Division broken into Mrkonjić-Grad on 26 October and, while small parties of the 3rd 'Sandzak' Brigade withdrew to the south-west, in the town the Germans seized 273 persons and took them to Jajce.
Near the village of Kozila, close to Jajce, Četnik forces destroyed the hospital of the 3rd 'Krajina' Partisan Detachment and murdered many wounded and some of the medical staff, including the doctors. The 3rd 'Sandzak' Brigade and the 3rd 'Krajina' Partisan Detachment then managed to withdraw to the Vitorog ridge area without suffering major losses.