During a battle Imam Ali (a) used to advise his followers in these words.
Do not allow a retreat to become so disastrous and overpowering as to make it impossible for you to remain firm at the battle. Do not be so disappointed and discouraged with a withdrawal or a defeat as to be unfit for a come back and a resumption of activities. Be bold, be courageous and allow your swords to do their duties and to justify your existence. Attack your enemies furiously and bravely and let them feel the full might of your arms and your hands. Impel and drive yourselves towards a dauntless and heroic courage and towards daring and undismayed use of your armaments. Do not shout but attack with eyes fixed on every movement of your enemy because you will thus dispel nervousness and cowardice.
I swear by the Lord Who allowed a seed to germinate into a plant and Who created these men who are opposing and facing you and who are fighting against you who did not embrace Islam but for securing a safety device for their lives and properties. They were not sincere in embracing Islam. It was done simply to provide for themselves a place in the growing and expanding power and position of the Islamic State. They would keep their paganism hidden to their hearts until they found their supporters and helpers. Only then they would come out openly.