Fun Fact: It's generally accepted that most flowery ancient pre-battle speeches are full of shit. A few which have survived, in whole or in part, which are considered reliable are generally short and sweet. Generals would need them to be so, since the most reliable way of imparting the speech would be to repeat it several times, each time before a group of a few thousand troops.
As Napoleon once noted, "It is not that addresses at the opening of a battle make the soldiers brave. The old veterans scarcely hear them, and recruits forget them at the first boom of the cannon. Their usefulness lies in their effect on the course of the campaign, in neutralizing rumors and false reports, in maintaining a good spirit in the camp, and in furnishing matter for camp-fire talk."