In History class we watched a video about the American Civil War, and in some of the reenactments the video depicted, there was always a man carrying a flag with a horn on his belt that charged into battle. He was not armed or anything. What was the point of this person, and why were they not armed?
This is mainly about control in battle (and proud to show your colors certainly). Now, picture this, lines of troops, may be"squares" several ranks deep walking towards the enemy line. They marched shoulder to shoulder, so the visibility for those behind the first line started to be poor, units tended to go in battle by regiments, so in the midst of the musketry discharges (black powder remember so whole lots of smoke all over the place), same for artillery firing upon you your visibility starts to decrease a lot. Not only for the private but for sergeants and officers trying to keep the ranks together.
So your line is broken by the enemy fire and you need to regroup as you march forward, what do you follow or take as a reference? The regimental flag ahead of you.
They were armed, I think is just a small error in the reenactment, but the flag pole would require both hands to carry and wave, they would have their rifles in their back with a leash. Needless to say that they marched ahead of the regiment so the casualties for the flag bearers must have been of very high proportion. Capturing an enemy flag was also an indication of courage and performance in battle, so you can imagine the rest.
Edit: typos