  We propose an approach to study non-Abelian Iwasawa theory, using the idea of
Johnson homomorphisms in low dimensional topology. We introduce arithmetic
analogues of Johnson homomorphisms/maps, called the p-Johnson
homomorphisms/maps, associated to the Zassenhaus filtration of a pro-p Galois
group over a Z_p-extension of a number field. We give their cohomological
interpretation in terms of Massey products in Galois cohomology.
