Translation of "Courier" in Spanish

Orders into action, by drafting written  instructions which were sent out by courier;  

órdenes del general , redactando instrucciones escritas que se enviaban por mensajería;

"“Yes,” said Bertrand, “I myself introduced by the back stairs to Napoleon the courier"

"“Sí, dijo Bertrand, “Yo mismo introdujé por las escaleras trasera a Napoleón al mensajero