Why did merlin paint himself blue, why did braveheart to?
There are many tactics used in battle. The most effective (according to Napoleon) is the psychological aspect of it.
An example being with the longbow and the gunpowder age. The longbow was much more effective at killing, it could be used from a long distance, it was more accurate, and in general, it was a lot better (in terms of killing) than the rifles around at the time. However, when soldiers were up against it, an arrow that went *doink doink doink* wasn’t very intimidating when put up against a *BANG BANG BANG* coming from rifles. When you add the psychological factor, the muskets were much more effective. Napoleon knew this, and exploited it.
To a lesser extent, that is why many armies had bagpipes playing while marching, and especially the drums. Any loud noise would begin to demoralize the enemy. Hence the drums and war cries. We’ve all got the fight or flight instinct, and all of the loud noise only serves to make us choose the ‘flight’ instinct.
This is also why (back to the original point) that people painted themselves. It served to demoralize the enemy (they were fighting with something that didn’t look human), and it served to confuse them. Many cultures had war paint, however in the case of Braveheart (William Wallace’s campaign in Scotland/England), it was for demoralizing.