One sign of the Messenger of Allah about the end times is the conquest of Constantinople for the last time. After that, the country Turkey will return to power of Muslims until the rising sun from the west.
When the conquest of Constantinople at the time of Sultan Muhammad Al-Fatih in the era of the Ottoman Caliphate occurred through a terrible war, with a large deployed equipment supported by most modern wars of his time; not the case with the conquest of Constantinople at the end of time that would happen in the era of Imam Al-Mahdi. The conquest of Constantinople after al-malhamah al-unsuccessful was an event out of the ordinary man. This unique conquest by 70,000 Bani Ishaq, without using the sword and spear, especially heavy weapons. They only use the Takbir and tahlil, the castle opened Constantinople. At the time of Al-Mahdi army were collecting ghanimah, occurred suddenly heard that the Antichrist has emerged.
The Prophet said, "Did you ever hear of a city located partly on land and partly in the sea? They (the Companions) said: Messenger of Allah Ever. He Saw said: It happened the day of Resurrection, so he was attacked by 70,000 people from Bani Ishaq. When they had got there, so they enter it. They are not fighting with guns and did not release any single arrows. They just say Laa ilaha illa Allaah akbar, then fell one part of the city. Said Tsaur (narrators of hadith): I do not know unless it is; only say that troops are in the sea. Then they say the second time Laa ilaha illa Allaah Akbar, then fell also some other (land). Then they said again Laa ilaha illa Allaah Akbar, then opened all of the city. Then they entered it. When they were handing out the war booty, suddenly there came a man (Satan), shouting: Behold the liars have been out. Then they left everything and come back. "HR. Muslim, Kitaab wa Asyratus Fitan Sa'ah
In another report mentioned that the Prophet was once asked, "Which city was conquered first, Constantine or Rome? Saw him then answered, "City of Heraclius will first be conquered. 
Who is the Bani Ishaq in history at the top? The authors of the slander end of the age difference of opinion about who is the Bani Ishaq. Someone mentioned that they were Romans who converted to Islam at the end of time, but some say that children are the descendants of Ishaq bin al-Aish Abraham ibn Ishaq. This opinion was chosen by Al-Haafiz Ibn Kathir. 
Know More Details About the Banu Ishaq
To find out who the Banu Ishaq, menelaaah back to the history books of the past, especially about the journey of the Prophet Abraham. As mentioned by Ibn Kathir, that is a descendant of the Bani Ishaq Al-Aish ibn Ishaq bin Ibrahim as. So very wrong those who say that the children of Isaac is the nation's Roman or Jewish descent who converted to Islam. To the Rum of the Prophet called them as children of Ashfar, some of them were converted to Islam in the era of Al-Mahdi, making friends with their compatriots were angry and wanted the Muslims to give them back. But the Muslims do not give up some of Banu Asfar who converted to Islam to the nation's Rum. Banu Ishaq is not the children of Israel. For the Children of Israel after its appearance is a prophet Ishaq.
Bani Ishaq mentioned as a liberator of the Prophet was a descendant of Constantine Ish bin Ishaq bin Ibrahim. While the Israelites were the descendants of Jacob ibn Ishaq ibn Ibrahim. They are the remnants of the Islamic army from Medina to win the battle against the Nation terdahsyat Rum in Malhamah Kubra. They say this is what the Prophet as the troops "will not be exposed to defamation forever or will not get lost forever". So, very wrong if Bani Ishaq are those Europeans who converted to Islam and joined al-Mahdi army.
The most logical possibility is a descendant of this Ish then spread on the territory of Khurasan (Afghanistan, Pakistan, Kashmir, Iraq and Iran). They are Muslims "when the news of Al-Mahdi had come immediately to greet and to help him. They are black flagged forces (ashhabu rayati Suud) which membai'at Al-Mahdi, and became his followers. Before the conquest of Constantine, they are Muslims who always accompany al-Mahdi in the conquest, including the conquest of the Arabian Peninsula.
Al-Mahdi's followers not only from ashhabu rayati suud, many other Muslims who join at the beginning of its appearance. But over time, some of them were not able to survive through life with Al-Mahdi, because the heavy burden that must be shouldered jihad. Peak pengkristalan Al-Mahdi army is in the event of war in Malhamah Kubra A'maq and Dabiq, where 1 / 3 of Al-Mahdi army and the retreat of the apostasy wars, 1 / 3 the troops get syahadah, and the rest is 1 / 3 of troops. Remaining forces that continue to endure with al-Mahdi in the next battle. Number of 1 / 3 that forces mentioned by the Prophet as the best human beings that live in the world. They come from the city of Medina. However, they are not the original inhabitants of Medina, they are Muslims who came from the east (Khorasan). In the conquest of the Arabian Peninsula, they kept winning, eventually for some time they lived in Medina.
So Banu Ishaq is a resident of Medina / residents who are faithful to accompany the Hijaz Al-Mahdi since they memba'iatnya. They are the owner of the black flags coming from Khurasan to strengthen the power of Al-Mahdi and liberate the Arabian Peninsula and settled in it for some time. This is the future of their country conquered Constantinople with 70,000 troops.
There are several texts which suggests that, where the population of Khurasan (Persian) will eventually replace the original Medina. They will reach what is promised by the Prophet to them. Did not he have said: 'If science (religion) is located in Tsuraya star, will undoubtedly reach the people of Persian descent. "
Prediction that the Arab population would be replaced by other nations has been mentioned by the Prophet in recent history, of which, as mentioned by Imam al-Tirmidhi in al Miskat:
When down verse 38 surah Muhammad, "If ye turn back (from religion)," 'He (God) will put (you) with other people, and they will not like you ", then some friends asked," O Messenger of Allah, if we turn, who will take the place (position) we? "He put his full blessing to the shoulders of Salman al-Farisi and said," He and his people (who will replace you). By the substance of my soul is in His hand, if religion is scattered on 'Tsurayya', then part of the Persian people will find it and hold it. "
In the above history, the friends worry after falling surah Muhammad verse 38. They worried that if it is replaced by the other. Thus, the companions asked Rasululllah "When we replaced the others, who are they, O Messenger of Allah?" So, the Prophet said, "Some of the Persians." Nash on the show that would replace the Arab nation is part of the Persian people, not the entire Persian . It could be Iranian Persian, or Afghan Persian or Persian Persian Pakistan or Kashmir. Allaah 'natural
It is they who will replace the position of Arabs in the Peninsula, until eventually they become the best people on earth who came from Medina. Through their hands and Constantine defeated Roman conquest.
When will it Happen?
Incident likely occurred in the days of Al-Mahdi, which Al-Mahdi's appearance is when people quarrel and fight, the condition of Muslims in general in the top of humiliation and continue didzalimi. While the Arab population of the world precisely because it carried away with the luxuries of life and the abundance of their wealth. Religion has a lot left and they've pledged guardianship to the west.
As a result, God replaced them with other people who do not like them. Based on these hadiths, then the people of Arab descent in the Peninsula will be replaced by his position by some Persian (probably the majority population of the region Khorasan Afghanistan, Pakistan, Kashmir and Iraq). This will happen in his time al-Mahdi. As mentioned in the hadeeth Ashabu Rayati Suud, the Prophet said, "I'll fight three people at perbendaharaanmu side. They all are sons caliph. However, none of them managed to master it. Then came the black flags from the east, then they fight you (the Arabs) with a war that has never experienced by the people before you. So if you see it, although with berbaiatlah crawling in the snow, because he is the Caliph of Allah al-Mahdi. "(Narrated by HR. Ibn Majah: Kitaab Chapter Khurujil Mahdi Fitan no. 4074)
So, Bani Ishaq was Persian (Khorasan). Imam Nawawi in syarahnya about 70 thousand children of Isaac argues that, "Population (Pharisees) Persians are the people who referred to the descendants of Isaac". Al-Mas'udi in his book titled Muruj ADZ-Dzahab argues, "People who understand about the pathways nasab Arabs and the hukama determined that the origin of the Persians are descendants of Isaac and Abraham's son.
Bish shawab Allaah knows best.