It is common in the Bible for people to "rise up," and it would be easy to pass over the phrase as simply describing a physical action. But in fact it represents an elevation in spiritual state, moving to a more internal frame of mind closer to the Lord. Often it has to do with understanding a new or important idea; we "rise up" to a state of greater perception and enlightenment. Obviously context is crucial to the exact meaning of the phrase in a given passage -- it matters greatly who it is that is rising up, and why.

524. "The nations were angry." (11:18) This symbolically means that people who were caught up in faith alone and thus in evil practices were enraged, and harassed those who opposed their faith.

Nations mean people caught up in evil practices, and abstractly, the evil practices themselves (nos. 147, 483). Here, however, it means people caught up in faith alone, because they are the subject here, and they are caught up in evil practices because their religion says that the Law does not condemn them, provided they have faith that Christ took away its condemnation.

Their being angry means, symbolically, not only that they were enraged, but also that they harassed people who opposed that faith of theirs, as can be seen from the description of the dragon in the next chapter, chapter 17, and later.