In the sixth year of the hijra, the Prophet decided to go for pilgrimage to Mecca. The Meccans stopped the Muslims at a place called Hudaybia and did not allow them to enter the city. This encounter ended in a peace agreement between the Prophet and the Quraysh of Mecca. This peace agreement created a relatively safe environment for the Prophet to embark on extending the call of Islam to the tribes and people far away from Arabia.
As a result of the activity of the Prophet and the selfless effort of the Muslims during that period, Islam spread through the Arabian Peninsula. There were also letters written to kings of other countries such as Persia, Byzantine and Abyssinia inviting them to accept Islam.
During this time the Prophet lived in poverty and was proud of it. He never spent a moment of his life in vain. Rather, his time was divided into three segments: one for God, in worshipping and remembering Him; a segment for himself and his household and domestic needs; and a segment for the people. During this part of his time he was engaged in spreading and teaching Islam and its sciences, administrating to the needs of the Islamic society, removing whatever evils that existed, providing for the needs of the Muslims, strengthening domestic and foreign bonds, and other similar matters.
One of the conditions of the peace treaty was that the Quraysh would not harm the Muslims or any of their confederates. This condition was, however, violated by the Quraysh when they helped Bani Bakr tribe against the Khuza’a tribe—the former an ally of the Quraysh and the latter an ally of the Muslims. The Prophet asked the Quraysh to respect the treaty, break their alliance with Bani Bakr and compensate the victims of their aggression. The Quraysh refused to abide by the terms of their treaty. The Prophet, with a well-equipped and well-disciplined force of about 10,000 soldiers, marched into Mecca in the eighth year after the hijra and conquered it without much resistance.
The city, which had rejected his message, plotted against his followers and conspired to assassinate him was at his mercy. Prophet Muhammad asked the Meccans: “What can you expect at my hands?” “Mercy! Generous and Noble Sire!” they replied. If he had wished, he could have made them all his slaves. But Muhammad —“mercy for the universe”— said: “I will speak to you as Joseph spoke to his brethren. I will not reproach you today; God will forgive you, for He is Merciful and Loving. Go, you are free!”
With the fall of Mecca, the last barrier in the way of Islam had been removed and many people and tribes of the Arabian Peninsula started accepting the message of Islam. Thus the ninth year of hijra is known as the “Year of Delegations” because of the unusual number of delegates coming to pay their homage to the Prophet at Medina.