The Conquest Of Makkah
merciful to whom? To the idolators who provoke attacks on innocent people, break treaties, kick out their own relatives, banned to participate in any sort of economical activities. Hostilites of quraish didnt stop after immigration they keep plotting. Being merciful to these type of people mean being unjust, breaking your own treaty etc. Also, prophets are sent for ihtemam e hujjat too. You have to keep that in mind. Prophet being conqurer depends from which perspective you see. Both are trying to survive depends on who perspective you see?