Then Franco decided to send Garcia Valiño's Maestrazgo Corps to the front and on 31 August the Nationalists launched an attack against the "Cavalls Range" in order to advance towards Corbera. The mountain range was held by the 35th, 11th and the 43rd Republican divisions, and the Nationalists attacked with eight divisions, 300 guns, 500 aircraft and 100 tanks. On 3 September the Nationalists launched a new attack from Gandesa supported by German 88 mm guns and by 4 September the Nationalists had occupied Corbera. Then Yagüe's forces broke the Republican lines, but Modesto sealed the breach with the 35th Division and ordered their troops to hold on: "Not a single position must be lost. If the enemy takes one, there must be a rapid counterattack and as much fighting as necessary, but always making sure that it remains in republican hands. Not a metre of ground to the enemy!" After six weeks of combat the Nationalists had recovered 120 square miles. On the other hand, on 21 September the Republican prime minister, Juan Negrin, announced the unconditional withdrawal of the International Brigades.