Battle of Badr
This success strengthened the resolve of the Muslims for, against the odds, they had won a decisive victory. Through military success and the astute use of marriage relationships (he had married A'ishah, the daughter of Abu Bakr and his own daughter Fatimah married Ali, who was to become the fourth Caliph), he increased cohesion amongst his followers and strengthened his position in Madinah.
But the ummah was still far from secure. There were pagan enemies in Madinah who rejected Islam and resented the power of Muhammad (peace be upon him) and his followers whom they saw as interlopers. There was a still more serious threat from the Makkans who, under Abu Sufyan, decided to expunge the humiliation they had suffered at Badr by wiping out the Muslim community. In 625 CE at Uhud, the Makkans joined battle with the Muslims and, although things went well for the Muslims initially, the Makkan gained the upper hand and defeated them.