'Sonnenwende' (i) was a German operation against the partisan forces of Marshal Josip Broz Tito in the area of Delnice and Lokve in German-occupied Yugoslavia (10/14 June 1944).

The operation pitted 1,500 men of Generalmajor Hubert Lamey’s 392^nd Division (kroatische) against the 13^th 'Primorsko-goranska' Division and, only one of several such operations, was designed to destroy the partisans' XI Corps in order to secure the area behind the Croat coast between Susak and Crikvenica and is one of several operations carried out along the littoral area. Because 13^th 'Primorsko-goranska' Division, whose staff Germans hoped to find in or around Delnice, was at that time in the Karlovac region, the Germans easily broke the defences of the 2^nd 'Primorsko-goranski' Partisan Detachment and entered Delnice, thereby ending the operation. However, the 13^th 'Primorsko-goranska' Division reacted quickly, despatching its 1^st Brigade back to the Delnice region. The brigade attacked Delnice immediately on arrival, forcing the Germans to retreat, but then failed to follow this success with any form of pursuit.

This gave the Germans the opportunity to regroup, and some 200 men and two tanks launched a counterattack that caused confusion in the partisan ranks and compelled the 1^st Brigade to retreat from Delnice. Only the brigade’s assault company remained in the town in an effort to drive back the Germans, who launched their final attack on the 1^st Brigade at 14.00. Following this, the Germans gathered their dead and wounded, and pulled back toward Lokve, their starting point.

The Germans claimed that their forces had killed 70 partisans in the first two days of fighting, while the partisans claimed to have killed 80 Germans and wounded another 110 while themselves suffering only 14 killed and 20 wounded. The operation changed little, but forced 13^th 'Primorsko-goranska' Division to change its plans so that its 1^st Brigade was ordered to attack Crikvenica in attempt to weaken the German threat to this partisan-held area.