The pro-German King Constantine dismissed the pro-Allied Prime Minister Venizelos on 5 October 1915, replacing him with Zaimis. On 5 October landings began at Salonika. Belgrade, the Serb capital, fell to the Central Powers on 9 October. On 12 October Sarrail arrived at Salonika and took command from General Bailloud. He at once ordered an advance to Strumica station, over the Serb border (Bailloud had previously been given contradictory instructions as to how far to advance). Under Serb pressure he agreed to advance as far as Krivolak, but not Skopje (capital of Macedonia, which was part of Serbia at the time), but was checked in the Vardar and Tcherna Valleys. His arrival had been too little and too late either to prevent German, Austro-Hungarian and Bulgarian forces overrunning Serbia, or to give the Serbs somewhere to retreat, ultimately forcing the Serb Army to retreat to Albania. He later wrote in his memoirs "one cannot do something with nothing". On 12 November Gallieni, now French War Minister in the new Briand government, ordered him to fall back on a fortified position around Salonika, but Sarrail replied that a retreat would be bad for prestige and would face resistance from Greek troops along the line of communication and at Salonika. Sarrail held his positions on the Tcherna for a week, hoping that the new French government would agree to build up his force from three divisions to four corps, and after receiving a dusty answer from Gallieni wrote to members of the government and appealed to Kitchener when he visited on 17 November. On 20 November Sarrail relieved a local commander who ordered a withdrawal, but on 21 November he was informed by Gallieni (who thought him "indecisive and not up to the task", but gave him liberty to decide when to retreat) that the French government would not be reinforcing him, leaving him little choice but to withdraw, and on 23 November he gave the order to pull back. By 12 December Sarrail's forces were holding a perimeter 20 km around Salonika. Sarrail forced the surrender of the Greek artillery in the town.