'Rouen' was a German, Croat and Hungarian operation against the partisan forces of Marshal Josip Broz Tito in the Kalnik Gora (mountain region) of German-occupied Yugoslavia (2/16 July 1944).
The object of the undertaking, in succession to the two 'Bienenhaus' operations, was to clear a large partisan force (elements of the 12th and 28th Divisions of the VI Corps and elements of the 32nd and 33rd Divisions of the X Corps) from the Kalnik Gora to the south-west of the line between Ludbreg and Koprivnica.
The Axis forces, under the command of General Helge Auleb’s LXIX Corps, were the German 2/4th Polizei-Freiwilligeregiment 'Kroatien', Croat headquarters, 1st and 2nd Regiments, Armoured Group, Artillery Battalion and elements of the Usta’e Non-Commissioned Officer School of Ustase Pukovnik Ante Moskov’s reinforced Poglavnik Bodyguard Division, three battalions of Ustase Pukovnik Rafael Boban’s 5th Ustase Brigade, one battalion of the 1st Traffic Control Brigade of the Ustase Militia, two battalions of Pukovnik Stjepan Grlić's 4th Mountain Brigade and the Reserve Group 'Kavalek', and from Hungary two regiments of an assault group, one reinforced regiment and one battalion of a blocking group, and one reinforced regiment (less one battalion) of a reserve group.
Although under overall German command, this large-scale operation was carried out almost entirely by Croat forces. The fighting was very heavy at times, especially in and around the town of Ludbreg, which was counterattacked during the night of 5/6 July by the 17th Assault Brigade of the 28th Assault Division, which was thrown back with severe losses.
The ring of Croat troops advancing from Bjelovar, Novigrad Podravski, Koprivnica and Krizevci finally closed on the centre of the Kalnik redoubt on 13 July, but the partisan main body slipped through the Axis cordon and escaped into the nearby Bilo mountain region. The Hungarian contingent that was supposed to take part in 'Rouen' was relegated to the Hungarian side of the Drava as a blocking force, to prevent any partisan escape across this river barrier, as a result of strenuous high-level objections by the Croats, who considered that any Hungarian presence on the western side of the Drava would represent an encroachment on Croat sovereign territory.
The Germans admitted the Croat loss of 158 men killed, 112 wounded and 23 missing, and claimed 1,017 partisan counted dead, a further 50 estimated dead, and 13 taken prisoner.