Moavia had not taken the oath of allegiance to Hazrat Ali (AS) as Caliph. His authority was scorned in his province, Syria. A terrible engagement with Moavia loomed in that direction. The Governor of Syria, Moavia flatly refused to comply with the orders of Hazrat Ali (AS), opposing Quranic Orders and Traditions in favour of Hazrat Ali (AS). It was a sort of open revolt. Hazrat Ali (AS) was reluctant to start hostilities against his rival lest it should defame the fair image of Islam. Before the adoption of strong measures, he wrote him a letter with these contents: “After praise to Allah and prayer for the Prophet (Suallu Alaihe Wa Aalehi Wasallam), let it be known to you why I overlooked you and did not ask you to swear allegiance to me immediately. In short, Usman (RA) was killed. It is a long story and I have no time to explain the situation fully. But whatever has happened, has happened. It cannot be retrieved. Now you must swear allegiance to me and come to me with your companions”.
In response to this letter, Moavia wrote: “Deliver unto us the assassins of Usman (RA) and the entire population of Syria will salute you. You, beyond all the doubts, are the most suitable person for the exalted office of the Caliph. The deceased Caliph has appointed me as Governor of Syria. The people of this province repose full confidence in me. They are not prepared to pay homage to you as their Caliph. I cannot go against the supporters of Usman (RA). I cannot betray the departed soul. I will never tender submission unless the murderers are traced out and severely punished”. The statement of Moavia is just like the statement of a thief, who thieves things himself and then conditions upon the people to search his stolen things and get the thief to him. Actually, Moavia was himself involved in the murder of the third Caliph Usman (RA) and was conditioning upon Hazrat Ali (AS) to provide the assassins of the deceased Caliph to him, then he will swear oath of allegiance of Hazrat Ali (AS). Marwan bin Hakam had close relations with Moavia who plotted the plan of murdering the third Caliph who had married Marwan’s sister Naila.
As Hazrat Ali (AS) was in favour of the peaceful settlement of this dispute, he left no stone unturned to convince Moavia. He wrote him another letter with these contents: “After praise to Allah and prayer for the Prophet (Suallu Alaihe Wa Aalehi Wasallam), let it be known to you that people are born in the world to do good deeds for the next world. This world is our examination place. We are created for trials and ordeals. And verily Allah has sent me against you. You accuse me of the murder of Usman (RA) which I never did with my own hands or tongue. I am not in any way connected with his murder. You have fabricated the story against me. You have been overcome by inordinate ambitions and foul temptations. You have started agitations against me for nothing. Be afraid of Allah lest some calamity should befall you. However, if fate decrees that I should confront you, I will not cease fighting against you unless the dispute is decided by Allah Who is the best Judge”.
On receiving the letter Moavia consulted Amr who was the conqueror of Egypt and an astute adviser of the headstrong Governor of Syria. Both of them declined to submit and acknowledge him as their Caliph. They decided to face the consequences. Upon this, Hazrat Ali (AS) had no alternative but to proclaim an expedition against Moavia to establish his authority. At first the people adopted an indifferent attitude towards both of them. It seemed as if they did not like to take sides in the dispute. They, in particular, were slow to answer the call of Hazrat Ali (AS) but afterwards they were prevailed upon to support the beloved son-in-law of the Prophet (Suallu Alaihe Wa Aalehi Wasallam) in the hour of dire need. They rallied round the Caliph in large numbers. Hazrat Ali (AS), however, succeeded in mustering a huge force which consisted of about 65000 soldiers. He marched towards Syria along the Euphrates. On reaching the upper part of Iraq, he crossed the river and stepped to the territory of Syria. On the other hand, Moavia lost no time in marshalling his forces which outnumbered the other army. Both the armies stood face to face in the plain of Siffin. They indulged in a few skirmishes. When the month of Muharram in 657 A.D. commenced, the fight came to a standstill. It was a pertinent time for the peaceful settlement of the dispute which had proved a bone of contention between both the parties. Some peace-loving sincere companions attempted to abhor war but their efforts were not crowned with success. Hazrat Ali (AS) had the support of Muhammad bin Abi Bakr, one of the regicides. He appointed him as the Governor of Egypt and removed Qais from his office. Qsis got angry and withheld from his favour. He shook hands with Moavia and became one of his camp followers. This step of the Caliph in dismissing Qais materially strengthened the hand of Moavia whose authority rested on a firm basis. The coalition of Moavia, Amr and Qais made their position most consistent. They had paramount influence on the ardent supporters of the innocent, Allah-fearing and pious Caliph Usman (RA) who was murdered in cold-blood by the favourites of Hazrat Ali (AS). On the other hand, the tempering attitude of Hazrat Ali (AS) towards the assassins complicated the situation and give birth to the sentiments of suspicion in the hearts of those who longed to take revenge for the murder of his predecessor.