TITLE: Examples of results first proved using geometrical methods?
QUESTION [6 upvotes]: Hi all,
I am beginning to learn about geometric group theory. I would like to write a little exposé intended to be read by the uninitated, so it would be nice to talk about (preferably simple) results which were inaccessible until geometric methods had been applied. Do you have suggestions?
Edit: I would also be interested to hear about results which aren't necessarily inaccessible otherwise, but admit simpler proofs within a geometric approach.
Best to all

REPLY [2 votes]: The proof of Stallings's Ends Theorem is topological.  Note that the set of ends of a group $\Gamma$ can be identified with $H^1(\Gamma,\mathbb{Z}_2\Gamma)$, so you don't have to define ends geometrically.