When Did The Islamic Conquest Of Jerusalem Begin?

The Prophet (peace and blessings of Allaah be upon him) drew the Companions’ attention to the liberation of the Levant and Jerusalem in many occasions and hadiths. The last army that the Prophet (peace and blessings of Allah be upon him) was preparing before his death was the army of Osama, who was in his way to The Levant ( Bilad Al-sham).