Meaning of "足生やす"


I was wondering if the above is some kind of expression or set phrase? I saw
this in in a novel actually where the speaker was remarking about his opponent
in battle who was summoning hundreds of soldiers loyal to him.

Edit: The line where the phrase in question is present goes like this

> こりゃ足生やした一個の『国』や。




This 足生やした not an idiomatic expression, but simply "(which) has grown legs" or
"(which) has legs". 足 is "foot" or "leg", and 生やす is "to grow" or "to wear (a
beard, etc)". He said the crowd of soldiers is almost like a walking country.
This is a rather unique metaphor.

