I'm writing a story and I would like to know how does the King pass on orders to his army. I want to walk readers through the process along which the King's orders leave his mouth and reach the ears of the soldiers who would be actually carrying over the order. How does this order pass through and finally get executed?
The matter of communication pops up every so often, though a search reveals that nobody's dealt with the Middle Ages specifically. However, the methods should not significantly differ, depending on how organised your army is. Thus:
u/Iphikrates comments on how the Greeks did it, in two threads: First thread, second thread.
u/Celebreth comments on the matter of control in this thread, directly related to the issuing of orders.