On May 15th, Operation Schwarz began, aimed at encircling and eradicating thousands of partisans operating around the Mostar area. After discussion with the Italian commander of the area, who, having received no orders to participate in the operation, wanted to deny their German allies the transit through his area, the Prinz Eugen forward elements eventually reached the Narenta at 0430 AM. The 1st Regiment, advancing southeast of Mostar, reached the eastern edge of Blagaj at 0815 AM with the II/1 8th Kompanie. While pushing forward, the first defenders started to show up.
