[p4] How do I obliterate a whole directory tree?

[P4 User]

I was trying to obliterate a directory.  The command "obliterate dir\*"
didn't work, nor did "obliterate dir\*\*", etc.  Turns out you have to
obliterate each branch of the directory that contains files with a series of
commands like "obliterate dir\*\*\*\*\*\*\*.*", followed by "obliterate
dir\*\*\*\*\*\*.*", followed by "obliterate dir\*\*\*\*\*\*.*", etc.
Basically go out to the furthest level of the directory tree and obliterate,
level by level, backwards, until all the files are gone.

Surely I'm missing something.  How do I obliterate an entire directory tree
with one command?