How did the functions of shields change over time? What were the functions of different shield sizes and shapes?
Some Medieval fantasy RPGs have rules regarding weapon types vs. armor types. Medieval fantasy RPGs also frequently have critical hit systems or charts that cover certain battle techniques. Back when I ran AD&D 2nd edition, we did initially make use of weapon type vs. armor type, but in the end it involved too much book-keeping and slowed down combat so we stopped. On the other hand, The Complete Fighters Handbook had a rich amount of combat tactics, melee maneuvers, and called shots, which we did enjoy using. I now use Castles & Crusades and enjoy using the combat maneuvers they have available (and as I page through my Complete Fighters Handbook in preparing this blog, I am reminded I could bring back a few more dynamic combat maneuvers from 2nd edition).
In the Modern History TV video, I have linked here (roughly 15 minutes long), Jason Kingsley covers three different shield styles and describes how they were used, and what modifications may have been made to them depending on whether the user was on foot, on horseback, or if they were using missile weapons (like crossbows). This is can add a rich addition to your RPG game for combat flavour and to open up the combat techniques available.
For example, the shield style used by the Vikings and Anglo-Saxons was more easily knocked aside by weapons in one-on-one combat, opening up the warrior’s chest and abdominal region for a thrust or a slash, yet they could be used more successfully together in a shield wall formation. However, once you move forward in time and the shields become smaller and more curved, then it was more difficult to knock it aside to open up the lone warrior to a blow, yet it also made them less effective for a shield wall (indeed, they were no longer using shield walls by then). In my C&C game I have a variety of cultures represented (Norse, Celtic, Knightly, Greek, Babylonian, Egyptian), so these cultural differences will allow me to bring in different styles of combat.
Enjoy the video, and perhaps you will find a way to add a unique twist to your RPG combat.