After the expulsion of the Jews of Bani Qainuqa and Bani Nadeer from Madina ,the policy of the Jews was to incite the Arab tribes to revolt against the Muslims. The Bedouin tribes of Banu Sa'ad and Banu Bakr which lived in the neighborhood of Khyber and Fidak were already hostile to the Muslims. The Jews incited them to attack Madina. They promised to provide them with arms and transport. Intelligence was brought to the Holy Prophet that these tribes were mustering a force and planned to attack Madina. The policy of the Holy Prophet was to strike before the enemy could strike and thus wrest the initiative from the enemy.