Al-Fath 48:3

In the sixth year of the Hijrah, the Prophet Muhammad left Madinah for Makkah along with his companions, so that he could perform the rite of pilgrimage there. He had reached Hudaybiyyah when the pagans of Makkah came forward and barred his way, saying that they would not allow him to enter Makkah. Mutual negotiations followed, as a result of which a peace treaty was drawn up and signed by both sides. This treaty was executed apparently on the unilateral terms and conditions dictated by the polytheists. As a consequence, the companions of the Prophet Muhammad were very disheartened: they considered it a degrading treaty. But on the way back from Hudaybiyyah, this verse was revealed, ‘We have granted you a clear victory.’ The reason for this was that according to this Treaty it was agreed that for ten years there would be no war between the Muslims and polytheists. The end of fighting was in fact synonymous to the opening of the door of dawah. After the Hijrah (migration to Madinah), due to incessant fighting, dawah activity had stopped. Now the truce had created an open atmosphere in which there could be a free exchange of thought between the opponents. In this way, this treaty changed the sphere of combat. Formerly, the competition between the two sides had been held on the battlefield where the Muslims’ antagonists had the upper hand. Now rivalry shifted to the field of intellect and in this, the theory of the one God clearly triumphed over polytheism. Here now was the ‘straight path’, i.e. the way which made the victory of the flag-bearers of monotheism an absolute certainty.