E.g. show all changes to pages under https://en.wikipedia.org/wiki/Wikipedia:WikiProject_Military_history .
The pages in that tree are listed at https://en.wikipedia.org/wiki/Special:PrefixIndex/Wikipedia:WikiProject_Military_history .
However, AFAIK there is no way to list recent changes to the tree.
I believe this can be done performantly with the existing rc_namespace_title index.