Venerable and experienced and still going strong at 200 years old, Charlemagne has spent his life conducting devastatingly successful campaigns in Spain and across Europe, expanding his empire while spreading the Christian faith. Everyone fears him and is in awe of him, even villains like Blancandrin, the Emir, Marsile, and Ganelon. As Marsile put it simply,
"I marvel greatly
At Charlemagne." (41.537-38)
And they don't even know about his supernatural powers. He receives dream-visions from God full of information that he often can't understand, and he is able to perform miracles, like making the sun to stand still (179). Then there is the angel Gabriel, who not only saves him from death during his fight with Baligant, but seems to follow him around like a faithful dog, giving pep talks and making signs of the cross (203, 261): "now there appears to him an angel who regularly speaks with him" (179.2452).
But Charlemagne is not quite as awesomely powerful as he first appears. His authority is limited in important ways, by self-imposed restrictions as well as things beyond his control.
Among the self-imposed are all the systems of feudal government set up in France. By gathering councils of his Twelve Peers he benefits from their advice, sure, but he also has to listen respectfully to their opinions and consider all options. Although he can dismiss their suggestions, like Duke Naimes's offer to go as envoy to Marsile, for some reason he can't or won't make his own suggestions. He jumps at the chance to send Ganelon to Spain, for instance, but refused to nominate himself (23).
Ganelon's trial is another example of the constraints on Charlemagne's decision-making. He wants Ganelon executed but is forced to abide by the jury's majority ruling. When Pinabel announces that they want to let him go,
His head and face sink down,
Because of the vexation he feels, he bewails his miserable lot. (277.3816-17)
Only by allying with Thierry can he eventually get the verdict he wants. Does this sound like the most powerful ruler in Europe? The Song of Roland emphasizes that Charlemagne's power is great but not absolute. Why? Because that's what the poem's 12th-century audience wanted to hear.
These French nobles were busy preserving the rights of the aristocracy and limiting the power of the Anglo-Norman kings, and they wanted French history to back them up. For more on how the poem reflects 12th-century ideals, click back to "Why Should I Care" or hit up "Setting."
In addition to government constraints, like the council and trial by jury, Charlemagne's power is also limited by things beyond his control, like Roland's stubbornness and Ganelon's treachery. Even Charlemagne's own religious devotion gets him into trouble, leading him to do whatever angels and God tell him to do. Gabriel says, Get up, and he does (203). Gabriel says, Go fight more pagans, and he has to, even though he cries and rips his beard (291).
All this makes Charlemagne vulnerable and melancholy as well as powerful and feared. He cries a lot and tugs his beard. He's often in positions of great anxiety without knowing what to do or feeling powerless. Remember his sadness when Roland joins the rearguard and he foresees the disaster but feels unable to stop it (67)? Or when he hears the oliphant and knows Roland is in peril but cannot reach him fast enough (136)? Or when he finds Roland's body and is so incapacitated by grief that he can't function for hours (205-11)?
The final touching scene drives the point home that being emperor is a double-edged sword, providing the power to do so much but also the grief and exhaustion of actually doing it. Charlemagne turns out to be an old sad man in an emperor's body. He doesn't want to fight any more battles or lose any more men. All he wants to do is sleep and grieve.
But he is also still Charlemagne, defender of the Christian faith, and thus cannot resist the angel. He must go on with the business of being the Holy Roman Emperor (291).
For more on why the ending is such a downer, click to "What's up With the Ending?"