The conquest of Persia took place during the era of the Commander of the Believers Omar Ibn al-Khattab, (may Almighty Allah be pleased with him), during his reign occurred the most important battles against the Persians, the battle of Qadisiyah, led by Saad bin Abi Waqas, and the battle of Nahawand led by Nu'man bin Muqrin,
Yes; during the reign of Caliph Abu Bakr, may Allah be pleased with him, open the country of Iraq, which was to that era under the control of the Persians.
Ibn Katheer (may Almighty Allaah have mercy on him) said:
"When Khalid Bin Al Waleed finished the Yamamah, the friend sent him to go to Iraq and start to liberate India, which is the goddess, and Iraq comes from the top, and that the people are composed and calls them to Allah Almighty. If they answer, or take the tribute from them, All of them fought in God, and ordered him not to hate anyone on the path with him, and does not seek help from those who converted from Islam, although he returned to him, and ordered him to take every man passed by the Muslims, and Abu Bakr in the preparation of Saraya and envoy and armies supply to Khalid, God is for him "End quote from" beginning and end "(9/511).
'They said: Muthanna bin Haritha bin Salamah bin Dhamd al-Shibani change the blackness in the men of his people, and reached Abu Bakr, may Allah be pleased with him, he asked him, he said to him Qais bin Asim bin Sinan al-Maqri: This man is not idle and male, , And not humiliated General: This Muthanna bin Haritha Shaibani.
And then that Muthanna presented to Abu Bakr, he said to him, O Messenger of Allah used me on the safest of my nation, I fight these Ajaj people of Persia, wrote Abu Bakr in that era, Vsar until Khavan came, and called his people to Islam Vslamoa, and then Abba Bakr (may Allah be pleased with him) wrote to Khaled ibn al-Walid al-Makhzoumi, ordering him to go to Iraq, and it is said: "His face is from the city." Abu Bakr wrote to al-Muthanna ibn Haritha, telling him to listen and obey him.
God sent Muhammad peace be upon him to all people Bashir and a warning. Allaah says (interpretation of the meaning): "And what We have sent you, but all to men, is a harbinger and a harlot, but most people do not know."
And Allaah says (interpretation of the meaning): "Say: O people, I am the Messenger of Allah to all of you, who has the King of the heavens and the earth. There is no god but He who gives life and death.
And he ordered him to report the message of Allah Almighty, he said: "O Messenger of God reached what was revealed to you from your Lord and if you did not do what you reached his message and God protects you from the people that God does not guide the people disbelievers.
And this reporting was possible only subject people under the authority of Islam to hear the words of God and his message without a barrier and no objection.
Allaah says (interpretation of the meaning): "O ye who believe! Fight those who curse you from the infidels, and find in you a hardness, and know that Allah is with the righteous."
It was narrated that Ibn 'Umar said that the Messenger of Allaah (peace and blessings of Allaah be upon him) said: "I ordered that I fight people until they testify that there is no god but Allah and that Muhammad is the Messenger of Allaah. They establish prayer and pay zakaah. If they do that, God) narrated by al-Bukhaari (25) and Muslim (22).
This is fighting to guide people to the religion of Allah Almighty; by putting the power that dominates them, and turning between them and the religion of God Almighty = put between two options: either to respond to the invitation of their Lord Almighty, or to give tribute and entry under the authority of Muslims.
Allah says (interpretation of the meaning): 'Fight those who do not believe in Allah or the other day, nor deny what Allah and His Messenger have forbidden, nor condemn the religion of truth from those who have given the Book.
This situation allows the landowners to hear the words of Allah at all times, and recognize the advantages of Islam, and gives them the opportunity to be taken to him after that voluntarily and convinced. Allaah says (interpretation of the meaning): "And if any of the polytheists hire you, then pay him to hear the word of Allah,
Al-Haafiz Ibn Hajar (may Almighty Allaah have mercy on him) said:
The scholars said that it is wise to put on the tribute that the humiliation that afflicts them and imposes them on entering into Islam with what is in contact with the Muslims is to learn about the virtues of Islam. End quote from Fath al-Baari (6/259).
This is what happened to most of the population of the countries conquered by the Muslims, whether in the Persian Empire or elsewhere.
One of the tasks of succession is to follow the caliph to the Prophet (peace and blessings of Allaah be upon him) in establishing the religion and communicating it to the people.
The point is that the friend Abu Bakr may Allah be pleased with him sought to open Iraq in response to the call of God to inform Islam to the people and save them from the misery of the world and the Hereafter.
God knows better.