Two other notable acts of brutality were the massacres of Italian troops at the islands of Cephallonia and Kos in September 1943, during the German takeover of the Italian occupation areas. In Cephallonia, the 12,000-strong Italian "Acqui" Division was attacked on 13 September by elements of 1. "Gebirgs-Division" with support from Stukas, and forced to surrender on 21 September after suffering some 1,300 casualties. The next day, the Germans began executing their prisoners and did not stop until more than 4,500 Italians had been shot. The 4,000 or so survivors were put aboard ships for the mainland, but some of them sank after hitting mines in the Ionian Sea, where another 3,000 were lost. The Cephallonia massacre serves as the background for the novel "Captain Corelli's Mandolin".