If you say that someone or something unleashes a powerful force, feeling, activity, or group, you mean that they suddenly start it or send it somewhere.
例句
Then he unleashed his own, unstoppable, attack...接著他開始了自己不可阻擋的攻擊。The officers were still reluctant to unleash their troops in pursuit of a defeated enemy.軍官們仍不愿發兵乘勝追擊潰敗的敵人。