While facing disasters at the Eastern front, Mehmed III died on 20 December 1603 at the age of 37. The new sultan Ahmed I who was 13 years old appointed Cigalazade Yusuf Sinan Pasha as the commander of the eastern army who marched from Istanbul 15 June 1604, a very late time for the campaigning season. Until he reached the front on 8 November 1604, the Safavid army had already captured Yerevan in June and advanced towards Kars before being stopped in Akhaltsikhe. Seeing the late season as an excuse, he did not counter-attack Abbas I and decided to stay in Van until the end of the winter. However, the Safavid advance forced him to march towards Erzurum. The inactivity created unrest among the Turkish ranks. His campaign of 1605 was unsuccessful, the forces he led towards Tabriz suffering defeat near the shore of Lake Urmia on 9 September 1605. This was the first Safavid pitched victory against the Ottomans in their history. In this battle Abbas I utilized his predominantly cavalry force to great advantage, decisively defeating the Ottomans, who suffered some 20,000 dead. Kose Sefer Pasha, Beylerbey of Erzurum, acted independently and was captured by Safavid forces. Cağaloğlu had to withdraw to the fortress of Van and thence in the direction of Diyarbakır. He ordered the execution of Canbulatoğlu Hüseyin Pasha claiming he was late to reinforce the Ottoman army which caused a larger unrest. Sinan  died in the course of this retreat in December 1605 and Abbas I was able to liberate Ganja, Baku, Shirvan and Shamakhi in Azerbaijan in June 1606.
Question: How many months after Mehmed III died did the eastern army march from Istanbul?
Answer: 6