Joan of Arc brings you back to the early 15th century when the 100 Years War is raging in France. As Joan of Arc, with the help of her French captains, you will battle the English across the countryside using both brains and brawn. The game is a hybrid between third-person action/adventure and real time strategy, and battles can take place between a handful of soldiers or entire armies besieging castles.
On the one hand, you've got simple hack and slash. As Joan or one of the more important French officers, you run around the French countryside (very linearly most of the time) and take it to the British the best way you know how; with iron to the face. Despite being a simple button masher, this can get interesting at times when more of your troops enter the fray against seemingly impossible British numbers.
The RTS portion usually takes place when a town or castle is being attacked. This is where you get to really take it to the enemy, or have it taken to you. You're given a set number of units, whether attacking or defending, and you must use them wisely throughout the course of the battle in order to attain victory.
Joan of Arc also has another aspect of play that meets somewhere in the middle of the previous two genres. While in your hack-and-slash mode, if you are accompanied by troops, you can have them follow you around the field of battle. This helps when you're in the middle of the RTS portion and you need to move a squad around in a precise maneuver; and how better than to get down into the trenches and do it yourself? This feature is the key that links the two seemingly unrelated genres together.