The Italians incurred 30,531 casualties during their occupation of Yugoslavia . The ratio of dead/missing men to wounded men was uncommonly high, as Yugoslav partisans would often murder prisoners. Their highest losses were in Bosnia and Herzegovina: 12,394. In Croatia the total was 10,472 and in Montenegro 4,999. Dalmatia was less bellicose: 1,773. The quietest area was Slovenia, where the Italians incurred 893 casualties. An additional 10,090 Italians died post-armistice, either killed during Operation Achse or after joining Yugoslav partisans.

Which country had the highest Italian losses, Montenegro or Croatia?
Croatia