How did the arbitration following the Battle of Siffin lead to the emergence of the Kharijites?

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2018). The mark or mark type is shown in brackets.

1. [10] The details of the arbitration drafted two days after the Battle of Siffin were a disaster for 'Ali as he had led his army into battle as the Commander of the Faithful and now the troops were headed back as a faction in a civil war, as the draft at the end read that both parties agreed to bind themselves by God's word. It could be said by the candidates that the disenchanted elements from 'Ali's army from both the Basra and Kufa regiments refused to set up camp with the rest of their regiment and they came to be known as the Kharijites. They were opposed to the idea of arbitration and argued for 'No judgment but God's', by which they meant that as the caliph 'Ali should not have agreed to the arbitration and compromised his authority. They were treated with compassion by 'Ali who reminded them that it was not him who had sought a ceasefire. The famous oath of Ghadir Khumm composed by the Prophet in the last year of his life was repeated. After which most of the Kharijites returned to their home. It was after the result of the peace conference held in 658 that the Kharijites got even more upset and set up their own community in Nahrawan. Later that year 'Ali's attempt to get the Kharijites on board to fight Mu'awiya was only partially successful as only 2000 moderates joined him. ‘Ali decided to deal with the remaining before confronting Mu'awiya but when 'Ali's army saw within the martyrs their fathers and brothers they lost the will to fight. Eventually 'Ali was forced to share power with Mu'awiya and the remaining small band of Kharijites raised the standard of rebellion in Persia.
2. [4] In response to this question candidates need to say if in their opinion the main reason for 'Ali' not winning the Battle of Siffin was on account of the Kharijites. The viewpoint of the candidate whether it agrees or disagrees with the statement given should be validated with reasons. Candidates could disagree by saying that the Kharijites only came into being after the Battle of Siffin, so could not be seen as the reason for 'Ali's defeat. Others could agree with the statement and say that the group who had propagated the cessation of fighting at Siffin later joined forces and came to be known as the Kharijites and dealing with them further weakened 'Ali's authority and resources. All valid responses to be credited.