I can easily see Serbia being in my next LP. Haven't had an opportunity to record Episode III yet.
But Serbia, man. There isn't really a counter to Hungarian foot knights, which is just a giant hassle. So far, the only success I've really had is through stringing their forces out across the entire country and trying to take them piecemeal, while another army goes around attacking the cities and castles.
B.H. Liddell Hart would be so proud of me.