'Adler' (iv) was a German and Croat two-part undertaking ('Adler I' and 'Adler II') against the partisan forces of Josip Broz Tito on the Dalmatian coast of Axis-occupied Yugoslavia in the area between Karlobag and Zadar, and in the Adriatic islands after the implementation of 'Achse' (ii) (11/26 November 1943 and 13 January 1944).

The twin operations were designed to secure Ugljan island, a useful base area, against its possible seizure by the Allies and its retention by the 'North Dalmatia' Partisan Detachment.

The undertaking had initially been posited, on 20 October, on the use of German forces to secure the east coast of the Adriatic Sea between Rijeka and Zadar, and involved Generalleutnant Karl Eglseer’s 114^th Jägerdivision, elements of Generalfeldmarschall Erwin Rommel’s Heeresgruppe 'B' advancing from the Rijeka region, parts of SS-Obergruppenführer und General der Waffen-SS Felix Steiner’s III SS Panzerkorps (germanisch) and the 14^th SS Polizeiregiment. This strength was changed to Generalleutnant Eduard Aldrian’s 373^rd Division (kroatische) and the garrison of Gospić to secure the coast from Karlobag to Novi in 'Adler I', and the 114^th Jägerdivision and Generalleutnant Johann Mickl’s 392^nd Division (kroatische) to clear Lika and the islands off Zadar in 'Adler II'. At one point the involvement of Generalleutnant Hermann Niehoff’s 371^st Division was also considered. Another variant of the basic plan called for the 114^th Jägerdivision to advance first to Gospić and Karlobag, and thence to Otočac and Novi to secure the coast.

During October it became clear to the partisan movement that any direct assault on Gospić garrison was becoming daily less feasible as the initial effects of the Italian capitulation dissipated and German reinforcements started to reach the area, so the decision was taken to blockade Gospić, leaving air drops as the only way for the Germans to supply their garrison. At the same time Tito decided to form the I Proletarian Corps for an advance into Serbia, and for this he requested from the command in Croatia that its best formation, the 6^th 'Lika' Division, should be diverted from the siege of Gospić and sent to Bosnia. To replace the 6^th 'Lika' Division, one division was ordered to move from Slovenia, but 'Wolkenbruch' prevented this, and the 13^th Division was ordered to send its units to positions around Perusić and the 19^th Division to send one brigade to southern Lika.

The departure of the 6^th 'Lika' Division and the arrival of Generalleutnant Albin Nake’s 264^th Division made it possible for the 114^th Jägerdivision to be used in several operations designed to push back the partisans in this littoral region. In overall terms, therefore, the undertaking’s objective was for the Axis forces to sweep and clear the partisan forces (13^th and 19^th Divisions and the 'Otočac' Partisan Detachment) from the coastal sector of northern Dalmatia between Gospić and Karlobag and thence north to Senj. The German contribution to the Axis force was the 114^th Jägerdivision and the 264^th Division, while that of the Croats was Ustase Pukovnik Čiril Čudina’s 4^th Ustase Brigade.

Ultimately the lack of adequate resources compelled the Germans to abandon 'Adler I' in favour of two smaller undertakings, namely 'Nibelungenfahrt' and 'Dreznica'.

'Adler II' was the second German offensive by Eglseer’s 114^th Jägerdivision and Mickl’s 392^nd Division (kroatische) on the Yugoslav partisan forces which had, since the time of Italy’s September 1943 armistice with the Allies, held the Croat coastal region, Lika and Gorski Kotar (13 January 1944). 'Adler II' was planned for implementation late in December 1943, but in fact started only on 13 January 1944 once the 392^nd Division had reached the area of Zagreb, Karlovac and Ogulin and started its advance toward Delnice and Senj in order to link with the 114^th Jägerdivision arriving from Dalmatia through Lika via Gospic, Otocac and Senj, in the course of which it fought the Yugoslav 13^th 'Primorsko-goranska', 19^th 'Dalmatia' and 35^th 'Lika' Divisions. At the operation’s successful conclusion, the 392^nd Division occupied positions along the Dalmatian coast from Novi to Senj and Karlobag.