  We develop a loop-loop correlation model for a unified description of static
color dipole potentials, confining QCD strings, and hadronic high-energy
reactions with special emphasis on saturation effects manifesting S-matrix
unitarity at ultra-high energies. The model combines perturbative gluon
exchange with the non-perturbative stochastic vacuum model which describes
color confinement via flux-tube formation of color fields. We compute the
chromo-field distributions of static color dipoles in various SU(N_c)
representations and find Casimir scaling in agreement with recent lattice QCD
results. We investigate the energy stored in the confining string and use
low-energy theorems to show consistency with the static quark-antiquark
potential. We generalize Meggiolaro's analytic continuation from parton-parton
to dipole-dipole scattering and obtain a Euclidean approach to high-energy
scattering that allows us in principle to calculate S-matrix elements in
lattice QCD. In this approach we compute high-energy dipole-dipole scattering
with the Euclidean loop-loop correlation model. Together with a universal
energy dependence and reaction-specific wave functions, the result forms the
basis for a unified description of proton-proton, pion-proton, kaon-proton,
photon-proton, and photon-photon reactions in good agreement with experimental
data for cross sections, slope parameters, and structure functions. The
obtained impact parameter profiles for proton-proton and longitudinal
photon-proton reactions and the impact parameter dependent gluon distribution
of the proton xG(x,Q^2,b) show saturation at ultra-high energies in accordance
with unitarity constraints.
