'Keulenschlag' was a German and Croat operation against the partisan forces of Marshal Josip Broz Tito in the Dreznica region of German-occupied Yugoslavia in the aftermath of 'Waldlauf' (14/22 April 1944).
The operation pitted Generalleutnant Johann Mickl’s 392nd Division (kroatische) against the partisans' 13th 'Primorsko-goranska' Division. The operation also targeted the now-large partisan infrastructure which had resulted from the Italian surrender of September 1943, and included hidden warehouses of weapons and ammunition taken from the Italian V Corps.
In the operation, whose results remain largely unknown, the 392nd Aufklärungsabteilung advanced from Senj to Tuzević and Dreznica; the 2/846th Grenadierregiment from Brinje to Gustovo Polje and Zrnić; the 3/846th Grenadierregiment from Brinje to Skalići; the 2/847th Grenadierregiment from Senj to Alan, Stalak and Jasenak; the 3/847th Grenadierregiment from Novi to Breza and Mosune; and the 33rd Ustase Battalion from Ogulin to Brezno.
The Germans claimed to have killed 86 partisans and to have captured two political commissars, one officer and 18 men. They also captured 93 tons of ammunition, three ex-Italian 105-mm (4.13-mm) howitzers, four ex-Italian 75-mm (2.95-in) guns, two ex-Italian 47-mm anti-tank guns, two light machine guns, 30 sub-machine guns, one mortar, 130 rifles, 30 trucks, and a number of military installations.