Kummer's work on cyclotomic fields paved the way for the development of
algebraic number theory in general by Dedekind, Weber, Hensel, Hilbert,
Takagi, Artin and others. However, the success of this general theory
has tended to obscure special facts proved by Kummer about cyclotomic
fields which lie deeper than the general theory. For a long period in
the 20th century this aspect of Kummer's work seems to have been largely
forgotten, except for a few papers, among which are those by Pollaczek
[Po], Artin-Hasse [A-H] and Vandiver [Va]. In the mid 1950's, the
theory of cyclotomic fields was taken up again by Iwasawa and Leopoldt.
Iwasawa viewed cyclotomic fields as being analogues for number fields of
the constant field extensions of algebraic geometry, and wrote a great
sequence of papers investigating towers of cyclotomic fields, and more
generally, Galois extensions of number fields whose Galois group is
isomorphic to the additive group of p-adic integers. Leopoldt
concentrated on a fixed cyclotomic field, and established various p-adic
analogues of the classical complex analytic class number formulas. In
particular, this led him to introduce, with Kubota, p-adic analogues of
the complex L-functions attached to cyclotomic extensions of the
rationals. Finally, in the late 1960's, Iwasawa [Iw 1 I] . made the
fundamental discovery that there was a close connection between his work
on towers of cyclotomic fields and these p-adic L-functions of
Leopoldt-Kubota.