I will present a description of saturation in small $x$ deep inelastic scattering from power counting in a top-down effective Glauber theory derived from QCD. The Glauber interaction breaks soft-collinear factorization and necessitates an expansion in the Glauber Hamiltonian. Factorization can then be proved order by order in the Glauber insertions. The resulting series of factorization formulas isolate the universal physics of the nucleus at leading power in $x$ and can be resummed under certain approximations. The onset of saturation in DIS is then understood as a breakdown in the expansion in an emergent power counting parameter, which is defined by the matrix element of a gauge invariant operator. We also demonstrate the presence of a novel collinear-soft radiation mode, which clarifies the role played by the medium size in deciding linear/non-linear evolution of the cross section in $\ln x$.