^In future, a time will come when Christians will rule most of the world and they would reach Khabr, then some from the family Abou Sufiyan (May Allah be pleased with him) will emerge and kill the king and take over the Arab. Meanwhile, in Europe, Christians will be divided in two groups and one of the group will become ally of the Muslim king in Arab. Then both of these groups will fight against the other Christian group and they will win. During the end of the battle a Christian soldier will say that we won due to the blessings of the cross (Christianity) but a Muslim soldier will say that we won due to the help and blessing of Allah. So they will start fighting and call for help. The war will erupt and Muslim king will be martyred during the battle. The Christian will take over the Muslim lands and will reach Khabr (near Medina) and both Christian parties will become ally again (1).

Then Muslims will start looking for Imam Mahdi (May Allah be pleased with him). Meanwhile, Imam Mahdi will appear and will try to avoid from people recognizing him (2). Eventually, one person will recognize him in Kahana Kaba. Finally, many Muslims will join him and he will build the army to fight against the Christians to get back Muslim lands.

wallahu a'alim (and Allah knows best)

Foot Notes
(1) this story has been reported in Sunan Abu-Dawud
(2) this has been also reported in Sunan Abu-Dawud and classified as sahih