Jackson: 1,000, and Beevor: 2,000 dead). Cartagena There was also combat in Ciudad Real and Cartagena. In Ciudad Real, Escobar's Extremadura Army crushed the communist resistance led by the deputy Martínez Cárton. Nevertheless, in Cartagena (the main base of the Spanish Republican Navy), where the supporters of Casado, backed by elements of a fifth column, had started the uprising against Negrín's government on 4 March, they were defeated by the PCE's 206th Brigade, of the IV Division, led by colonel Joaquín Rodríguez, after a brief battle on 7 March. Nevertheless, on 5 March, the Republican Navy (three cruisers and eight destroyers), led by Admiral Buiza, had fled to Bizerte after a Nationalist aerial bombardment. One Nationalist transport ship, the Castillo de Olite, sent by the Nationalists in order to support the uprising, was sunk by the coastal batteries of Cartagena, killing 1,200 Nationalist soldiers. Peace negotiations with Franco After the defeat of Barceló's troops, the council tried to start peace negotiations with Franco, hoping to achieve a guarantee against political reprisals. On 12 March, the council proposed a peace deal with a guarantee against reprisals and a period of 25 days to allow anyone who wanted to leave Spain to do so. On 16 March, Franco answered that he would only accept an unconditional surrender. On 23 March, the council sent two negotiators to Burgos (Colonel Antonio Garijo and Major Leopoldo Ortega), and the Nationalists told them that on 25 March, the Republican Air Force had to be surrendered and by 27 March, the Republican troops had to raise the white flag. Nevertheless, on 25 March, the Republicans did not surrender their Air Force because of bad weather and Franco then broke off negotiations with the junta. Final offensive On 26 March, Yagüe's troops advanced in Sierra Morena. There was no resistance, and in one day they captured 200,000 km2 of land and 30,000 prisoners. The junta ordered its soldiers not to resist the Nationalist advance, and the Republican soldiers threw away their weapons and abandoned the front. By 27 March, the Nationalists were advancing on all fronts without resistance. Solchaga's Navarra Corps, Gambara's CTV and Garcia Valiño's Army of Maestrazgo advanced from Toledo. On 28 March, Colonel Prada, commander of the Army of the Centre, surrendered to the Nationalist troops, who occupied Madrid. Casado and the other members of the junta, except Besteiro, fled to Valencia. On 29 March,