One theme the two epic poems The Song of Roland and Nibelungenlied, from the Middle Ages, share in common is chivalry.
In The Song of Roland, the protagonist Roland becomes devoted to protecting Charlemagne because, from the start, Charlemagne tested Roland's courage. Roland's mother is Charlemagne's sister, Princess Bertha, but the family has been treated with disrespect because Charlemagne considers Roland's father, Milon, as having stolen Charlemagne's sister from him. After his father is killed by Charlemagne in battle, when given the opportunity, Roland marches into Charlemagne's banquet hall and demands provisions for himself and his mother. Charlemagne, happy to have his sister back, immediately gives them honorable positions at court. Roland in particular is made a squire. Soon, Roland's bravery as a squire is tested, and Roland saves Charlemagne's army by posing as the enemy and attacking the enemy from within. Roland is immediately knighted and given the famous sword Durandal and the battle horn of his grandfather. Roland also vows to always protect Charlemagne; hence, at another moment when Roland is attacked by a traitor, Roland decides not to blow the battle horn to summon Charlemagne's troops for reinforcements because he doesn't want to put Charlemagne in harm's way. Instead, he sees himself as responsible for fending off the traitor. Sadly, the mistaken decision costs Roland his life, but Charlemagne does indeed remain alive. Hence, we see that Roland's story is one of devoted bravery and captures the theme of chivalry since acting in bravery is part of the chivalric code.
Similarly, in Nibelungenlied, Gernot behaves chivalrously when he prevents Gunther and Siegfried from battling each other. Gernot further acts chivalrously when welcoming Siegfried to Worms with open arms. Soon, Siegfried is given his own opportunity to act chivalrously when he fights with his troops as allies to the Burgundians under Gunther the moment the Burgundians are attacked by King Liudegast of Denmark and King Liudeger of Saxony.