There’s no direct evidence that I know of that Longstreet’s artillery chief, Colonel Edward Porter Alexander, used signal flags at Knoxville to, for instance, alert the Boy Battery on Cherokee Heights when to cease fire. And also the other batteries of his command which were arranged on a long line north and east of his headquarters near the Holston River.
But I decided in writing the novel that it was just common sense to assume that Alexander used semaphore, when the weather allowed. It was used in many other instances in the war on both sides. Couriers, whether on horseback or on foot, took time. There’s no evidence that telegraph was available to the Rebels at Knoxville. Flags were quick. And after all, who would know better how to use them and teach his officers how to read them than Alexander?
He had worked as a post-graduate assistant at West Point with Major Albert J. Myer, the inventor of the wig-wag system. Myer created the U.S. Army’s first Signal Corps, which became so prominent that, after the war, it assumed control of national weather forecasting. Alexander had pioneered Confederate use of the signal flags at the first Battle of Manassas.