According to the terms of the treaty of Hudaibiya the Arab tribes had the option to be allied with the Quraish or the Muslims. As a consequence the Banu Bakr joined the Quraish, and the Khuza'ah joined the Muslims.
In disregard of the treaty, Banu Bakr attacked the Khuza'ah and even when the Khuza'ah sought the sanctuary of the Ka'aba, many persons of the Khuza'ah were chased and put to death.
The Khuza'ah wanted the Muslims to come to their aid in accordance with the terms of the treaty. The Holy Prophet gave an ultimatum to the Quraish making three alternative demands, i.e.
(1) to pay tne blood money for the victims;
(2) to terminate their alliance with Banu Bakr; or
(3) to consider the Hudaibiya pact to be abrogated.
In a fit of arrogance the Quraish replied that they would neither pay blood money, nor terminate their alliance with Banu Bakr, and that they were prepared to consider the Hadaibiya pact as having been abrogated.
The Muslims in general and Umar in particular were happy that the Hudaibiya pact of which they were critical had been abrogated by the Quraish themselves.
The Quraish soon realised that they had imprudently abrogated the treaty. Abu Sufiyan the leader of the Quraish visited Madina to arrive at some amicable settlement. He wanted his daughter who was a wife of the Holy Prophet to plead for him with the Prophet but she refused. Abu Sufiyan waited on Abu Bakr and Ali but they did not listen to him. He sought the help of Umar, and lJmar made him understand that there could no longer be any reconciliation with the Quraish unless they accepted Islam. The peace efforts having proved futile, Abu Sufiyan returned to Mecca.
After Abu Sufiyan had left Madina, the Holy Prophet ordered preparations to be made for a foray. As Umar came to see his daughter Hafsa, he saw that she was packing some goods. He enquired whether Holy Prophet had ordered her to get things packed up, and she said that he had. Later the Holy Prophet took Umar into confidence and told him that he was leading an expedition to Mecca, and that he was also to accompany him.
The Holy Propllet mustered a force over ten thousand strong and marched to Mecca. Having reached the neighbourhood of Mecca the Muslim army encan~ped at Marr al-Zahran
The Holy Prophet sent liadrat Abbas to Mecca on a diplomatic mission. Haclrat Abbas met Abu Sufiyan and advised him that the best course for him and the Quraish was to place themselves at the mercy of the Holy Prophet. Abu Sufiyan agreed to wait on ~he Holy Prophet to get terms.
Umar saw Abbas and Abu Sufiyan proceeding to the camp of the Holy l'rophet. Iladrat Umar strode forward l~urriedly, and addressing the Holy Prophet said. "Permit me to behead Abu Sufiyan the enemy of Islam." The Holy Prophet said, "Umar, wait for a while and see."
At the Muslim camp, Abu Sufiyan was converted to Islam. That was the end of the Quraish opposition.
The following day the Muslim army marched triumphantly into Mecca. One of the contingents was lead by Umar.
The triumphant entry of the Muslims in Mecca marked the vindication of the truth of Islam. The city which ten years ago had treated the Muslims cruelly, and had driven them to seek refuge with strangers, now lay at the feet of the Muslims.
In the hour of triumph the Holy Prophet forgot every evil suffered, and forgave every injury that had been inflicted on him. He granted general amnesty to the people of Mecca.
The Holy Prophet along with his companions visited the Ka'aba. The idols were broken, and one by one the stone gods were destroyed. Thereupon the Holy Prophet recited the verse from the Holy Quran:
"Say the Truth is come and falsehood gone; Verily faslehood is ever vanishing."
The people assembled at the Ka'aba, and the Holy Prophet delivered the following address:
"There is no god but Allah. He has no associate. He has made good His promise that He held to his bondman and helped him and defeated all the confederates. Bear in mind that every claim of privilege, whether that of blood or property is abolished except that of the custody of the Ka'aba and of supplying water to the pilgrims. Bear in mind that for any one who is slain the blood money is a hundred camels. People of Quraish, surely God has abolished from you all pride of the time of ignorance and all pride in your ancestry, because all men are descended from Adam, and Adam was made of clay." Then the Holy Prophet turning to the people said:
"O ye Quraish, what do you think of the treatment that I should accord you.?"
And they said, "Mercy, O Prophet of Allah. We expect nothing but good from you."
Thereupon the Holy Prophet declared:
"I speak to you in the same words as Joseph spoke to his brothers. This day there is no reproof against you; Go your way, for you are free."
The announcement was received with greatest joy and applause. Then accompanied by Umar the Holy Prophet ascended the brow of the Safa to initiate the people to the vow of allegiance to Islam. The people came in large numbers to be converted to Islam. After the oath-taking ceremony of men was over, the Holy Prophet directed Umar to take the oath of allegiance from women on his behalf. All the Quraish ladies in Mecca took the oath of allegiance to Allah, the Holy Prophet and Islam at the hands Umar.