[Rumil]

I've always reckoned that the relief of Gondor by the Rohirrim was partly inspired by the crusades, except with a happy ending this time!

Gondor representing Byzantium, one half of a formerly great and powerful Empire now to an extent decayed and under threat from the Turks and Saracens, but with the Rohirrim, a force of chivalric hard charging knights riding to their rescue (not that the crusaders were mostly chivalric or knights and they eventually ended up sacking Byzantium, but you get my drift!). Also an element of the relief of Vienna by the Poles maybe?