 However, a number of German and Romanian units that were to take part in "Blau" were besieging Sevastopol on the Crimean Peninsula.Delays in ending the siege pushed back the start date for "Blau" several times, and the city did not fall until early July.Operation Fridericus I by the Germans against the "Isium bulge", pinched off the Soviet salient in the Second Battle of Kharkov, and resulted in the envelopment of a large Soviet force between 17 May and 29 May.