 Between 11 – 13 April 1941 , with German and Italian troops advancing on its rear areas , the Zetska Division was forced to retreat back to the Pronisat River by the Italian 131st Armoured Division Centauro , where it remained until the end of the campaign on 16 April . The Italian armoured division along with the 18th Infantry Division Messina then advanced upon the Yugoslav fleet base of Kotor in Montenegro , also occupying Cettinje and Podgorica . The Yugoslavs lost 30 @,@ 000 men captured in the Italian counterattacks . 
