2 Samuel 15:10-11

10Then Absalom sent his men to go secretly to all the tribes of Israel. They took this message to the people: ‘When you hear the noise of trumpets, then you must shout, “Absalom has become king in Hebron.” ’

11200 men had gone with Absalom from Jerusalem. He had asked them to go with him as his friends. They trusted him and they did not know about his ideas.