Why does lee tell Longstreet to stay back from the main line in the battle to come?

Lee instructs Longstreet to stay back from the main line to ensure he can observe the battle from a distance and maintain overall command. By doing so, Longstreet can analyze the unfolding situation and make strategic decisions without being directly involved in the chaos of the front lines. This separation allows Lee to utilize Longstreet's military experience and judgment more effectively, ensuring that key decisions are made based on a broader perspective of the battlefield.