Remember the battlefield in which you were in the higher grounds of the valley and they were in the lower side of the valley (destined to suffer from the rain that was sent before the battle) and the caravan was below you. Even if you had agreed to meet each other, you would have not come to the battlefield (as you were low in number and ill-equipped] but God had decided to accomplish His plan and let whoever had to perish to perish and whoever deserved to live to live; thus sending a clear message. Indeed, God hears and knows everything.