Mu'awiya is thus in breach of a solemn oath he took not to...
Mu'awiya is thus in breach of a solemn oath he took not to make the khilafat a monarchy by appointing his own son as Crown Prince. Imam Hassan (as) made peace to avoid bloodshed This issue is fundamentally tied up with the forced abdication of Al-Hassan (as) as khalifa in the face of Muawiya's rebellion against Imam Hassan (as)'s lawful and noble khilafat.
Al-Hassan (as)'s is deemed by Jalal-ud-din Suyuti in his established Sunni account of the khilafat the fifth rightly guided khalifa, and while most Sunnis have not heard this he ruled for six months and was by their scholars rightly guided.
For this section we shall focus on the following texts of Ahl'ul Sunnah: Irshad al Sari Sharh Bukhari Volume 1 page 198 Bab ul Fitan Umdah thul Qari fi Sharh Bukhari Volume 11 page 361 Kitab al Fitan Murqaath Sharh Mishqat Volume 11 page 379 Al Istiab Volume 1 page 370 For the sake of brevity we shall cite al Irshad: "Imam Hasan did not abdicate on account of any bribe / wordly gain or weakness; rather he made peace so as to avoid fitnah and bloodshed." Mu'awiya had agreed that the Khilafat would return to Imam Hasan (as) when he died This is undeniable and is testified to, amongst numerous other Sunni works, in: Fathul Bari fin Sharh Bukhari Volume 3 page 65 Kitab al Fitan Mirqat Sharh Mishqat Volume 11 page 38 Bab Manaqib Ahl'ul Bayt Al Bidayah wa al Nihaya Volume 8 page 80 events of 57 Hijri Hayaath al Haywaan Volume 1 page 53 Dhikr Khilafa Tareekh Khamees Volume 2 page 29 Dhikr Hasan Al Imama wa al Siyasa page 18 Sulh Hasan Al Istiab Volume 1 page 370 Dhikr Hasan For the sake of brevity we shall cite al Bidaya: "At the time of the peace treaty, Mu'awiya agreed that the khilafat would return to Hasan when he died" In Fathul Bari we read: "At the time that the peace treaty was agreed Hasan stated that 'I have made this treaty on the condition that after Mu'awiya I succeed as Khalifa'.
The fact that Mu'awiya wanted to make Yazeed his successor was hugely embarrassing for him, since this contravened the peace treaty and hence the better option would be to remove Imam Hasan (as) (this has been discussed in our article on Mu'awiya). In the meantime Mu'awiya's flagrant breach of the treaty continued. This is an embarrassment for the Nasibis as this treaty and its terms are not controversial and accepted by all.