Muawiyah ibn Abu Sufyan (Moawiya) was ruling over Syria as its Governor for nearly sixteen (16) years; and was secretly planning to grab the Caliphate taking advantage of every possible opportunity. The best excuse for him to revolt against the Central authority and declare his own caliphate was the third caliph Othman bin Affan's murder. Muawiyah ibn Abu Sufyan had not done any thing concerning the appeals of caliph Othman bin Affan for help, during his lifetime. In fact, he was waiting for him to be murdered, so that he could make it an excuse for his scheme. Caliph Othman bin Affan (Osman bin Affan) got murdered and Muawiyah immediately sought to exploit the situation for his own purpose.
On the other hand, people after the murder of caliph Othman bin Affan rallied behind Imam Ali ibn Abu Talib (as) (who because of various reasons, was reluctant to take the responsibility of Caliphate) and declared their allegiance to him. Observing that the responsibility was now formally turned to him, Imam Ali ibn Abu Talib (as) accepted it and his Caliphate was proclaimed in Medina, the capital and centre of Muslim world in those days. All provinces of Islamic government submitted to his obedience - with the exception of Syria, which was under Muawiyah ibn Abu Sufyan. He refused allegiance to Imam Ali ibn Abu Talib (as), accusing him of sheltering the murders of caliph Othman bin Affan. Muawiyah recruited a large number of Syrian soldiers and made preparation for the declaration of independence of his provinces.
After settling the issue of the battle of Camel (Jange Jamal), Imam Ali ibn Abu Talib (as) turned his attention to Muawiyah ibn Abu Sufyan. He wrote several letters to him, but in vain. Both sides moved their armies towards each other near Siffin. Abul Aawar Salmi was leading Muawiyah's advanced battalion and Malik Ashtar was in command of the advanced battalion of Imam Ali ibn Abu Talib (as). They met at the bank of the Euphrates. Imam Ali's (as) directive to Malik Ashtar was not to be the first to attack. But Abul Aawar Salmi made a severe attack to intimidate the soldiers of Imam Ali ibn Abu Talib (as). Malik Ashtar then pushed the Syrians far behind. Abul Aawar Salmi now thought of another tactics. He reached the Ghat, i.e. the slope on bank of the Euphrates, which was the only spot convenient to fetch water. Abul Aawar Salmi deployed his spearmen and archers to guard the spot and prevent Malik Ashtar and his company from coming near it. Soon after, Muawiyah ibn Abu Sufyan himself arrived with a large army. Happy at the strategy of his commander he further increased the number of the soldiers guarding the approach to river. Soldiers of Imam Ali ibn Abu Talib (as) were put in distress owing to the shortage of water. Muawiyah with pleasure said: "This is our first Victory." Only one man, Amr bin Al-Aas, the shrewd minister of Muawiyah ibn Abu Sufyan did not think it a good policy. On the other side, Imam Ali ibn Abu Talib (as) himself had arrived and was informed of the situation. He sent a letter with Sasha bin Suhan, one of the companions (Sahabi) of Prophet Muhammad (saw) to Muawiyah notifying:
"We have come here, but as far as possible we do not like to wage a war of fratricide between the Muslims. We earnestly hope to settle our differences through negotiations and discussions. But we observe that you and your followers have started using weapons of destruction before trying anything else. Besides, you have denied water on my companions. Instruct them to desist from this act, so that we can start negotiations. Of course, if you do not like anything but war, we are not afraid of it."
Muawiyah ibn Abu Sufyan consulted his advisor. The general opinion was to take advantage of the golden opportunity and ignore the letter. Only Amr bin Al-Aas against this view. He said, "You are mistaken." The fact is that Imam Ali ibn Abu Talib (as) and his men do not want to start the war themselves, and it is because of this that they are silent at present and have tried to dissuade you from your scheme through this letter. Do not think they will retreat if you ignore their letter and continue denying them the water. Because then they will take out arms and will not stop till they have driven you away from Euphrates with disgrace." But the majority of advisors were of the opinion that the denial of water would weaken the enemy compelling them to retreat. Muawiyah ibn Abu Sufyan personally was in favor of this idea. Discussion came to end; Sasha bin Suhan, one of the companions of Prophet Muhammad (saw) asked for the reply; Muawiyah ibn Abu Sufyan, using the delaying tactics, said that he would send the reply afterwards. Meanwhile, he ordered his soldiers guarding water to be extra alert and to prevent coming and going of the soldiers of Imam Ali ibn Abu Talib (as).
Imam Ali ibn Abu Talib (as) was distressed at this development, because it brought to an end every hope of any amicable settlement through talks and negotiations, and showed that the opposite side was devoid of every goodwill. Now, the only way out was to use force. Imam Ali ibn Abu Talib (as) stood before his soldiers and delivered a short but forceful address, the contents of which were as follows:
"These people have started oppression, and opened the door of conflict and welcomed you with hostility. They are hungry for war and are demanding war and bloodshed from you. They have denied you water. Now you have to choose between the two paths. There is no third course. Either accept the humiliation and oppression or remain thirsty as you are, or satisfy your thirsty swords with their dirty bloods so that you may quench your thirst with the sweet water. Death is to live a defeated and disgraceful life; and Life is to be victorious even at the cost of death. Verily, Muawiyah has gathered around him some ignorant and misguided mob; and is taking advantage of their ignorance, so that they are making their necks targets of the arrows of death."
This address moved the soldiers of Imam Ali ibn Abu Talib (as) and stirred their blood. They made a severe attack and pushed the enemy far back and took the possession of Ghat.
Amir bin Al-Aas (whose forecast was now a fact) said to Muawiyah ibn Abu Sufyan: "Now, if Imam Ali ibn Abu Talib (as) and his army pay you with your own coin what will you do? Can you take possession of the Ghat from them for the second time?" Muawiyah said, "In your opinion, how will Imam Ali ibn Abu Talib (as) deal with us now?"
"I believe, Imam Ali ibn Abu Talib (as) will not behave as you had done. He will not deny us water. He has not come here for such deeds."
The soldiers of Imam Ali ibn Abu Talib (as) after removing the soldiers of Muawiyah ibn Abu Sufyan from Ghat, asked his permission to prevent the enemy from taking water. Imam Ali ibn Abu Talib (as) said, "Don't deny them water. These are the methods of ignorant. I do not set my hands to such acts. They are human beings and though they have acted inhumanely yet I cannot follow their example and cannot refuse a man food and drink because he happens to be my worst enemy. I am going to start negotiation with them on the basis of the Holy Book of Allah (SWT). If they accept my proposals, well and good; and if they refuse, I shall fight with them, but gentlemanly not by denying them water. I will never do such thing and will not oppress them by shortage of water."
Not long afterwards soldiers of Muawiyah ibn Abu Sufyan used to come to the Ghat side by side with the soldiers of Imam Ali ibn Abu Talib (as), and nobody prevented them.