Saxons, Slavs, Huns, Lombards, Arabs, came under his compelling grasp; these antagonistic races all held together by the force of one terrible will, in unnatural combination with France.

No political liberties, no popular assemblies discussing public measures; it is Charlemagne alone who fills the picture; it is absolutism--marked by prudence, ability, and grandeur, but still, absolutism.
The pope looked approvingly upon this son of the Church, by whose order 4,500 pagan heads could be cut off in one day, and a whole army compelled to baptism in an afternoon.

Here was a champion to be propitiated.

Charlemagne, on the other hand, saw in the Church the most compliant and effective means to empire.
His fertile mind was conceiving a vast design by which he might reign over a resuscitated Roman Empire.

In the dual sovereignty of his dream, the pope was to be the spiritual and he the temporal head.
Mutually dependent upon each other, the election of the pope would not be valid without his consent.