TITLE: Relation between Tate's thesis and Class Field Theory
QUESTION [8 upvotes]: Class Field Theory states the correspondence between abelian extensions of k and congruence divisor class.  In idelic language, there is a surjective map from $J_k/k^*$ to $Gal(k^{ab}/k)$ with its kernel unkonwn.
Tate's Thesis proved some functional equations and analytic continuity(with a finite character of $J_k/k^*$). 
Question: Why Tate's thesis contributed to class field theory?

REPLY [3 votes]: Boyarsky has already answered the question in the comments section.  These are a couple of expositions which put John Tate's contribution in perspective.

Stephen Kudla's chapter on Tate's
thesis
Stephen Gelbart's article on Elementary
introduction to Langlands'
program.  See the section beginning page 194