After the battle of Jamal was over, Imam Ali (A.S.) returned from Basra to Kufa in Rajab of 36 A.H. He decided to transfer the capital of his government to Kufa from Madina because it was more centrally placed in the Muslim Empire, and he could halt Muawiya's progress into Iraq.
Before marching towards Muawiya, Imam Ali (A.S.) tried to settle matters peacefully by sending Jarir, chief of Bani Bajila and the governor of Hamdan, to Syria as an envoy. However, Jarir became so engrossed in the entertainment that Muawiya put his way, that he wasted his time in Syria. He finally returned three months later with the useless message that peace could only be negotiated if the murderers of Uthman were brought to justice. Malik al-Ashtar accused him of having wasted time in effeminate pleasures with Muawiya, who purposely kept him long enough to mature his plans of hostilities. Jarir left Kufa and joined Muawiya.
Imam Ali (A.S.) decided that matters could be only decided by war, so he marched without delay through the Mesopotamian desert to Riqqa at the banks of the Euphrates. After crossing the river by constructing a bridge they came across the Syrian outposts at Sur al-Rum. There were a few skirmishes between the armies but the Syrians gave way and in the month of Zilhaj of 36 A.H., the army of Imam Ali (A.S.) came into sight of Muawiya's main forces, which had already camped at Siffin.
source : http://www.ezsoftech.com
