  We develop an approach to the high-energy limit of gauge theories based on
the universal properties of their infrared singularities. Our main tool is the
dipole formula, a compact ansatz for the all-order infrared singularity
structure of scattering amplitudes of massless partons. By taking the
high-energy limit, we show that the dipole formula implies Reggeization of
infrared-singular contributions to the amplitude, at leading logarithmic
accuracy, for the exchange of arbitrary color representations in the cross
channel. We observe that the real part of the amplitude Reggeizes also at
next-to-leading logarithmic order, and we compute the singular part of the
two-loop Regge trajectory, which is universally expressed in terms of the cusp
anomalous dimension. Our approach provides tools to study the high-energy limit
beyond the boundaries of Regge factorization: thus we show that Reggeization
generically breaks down at next-to-next-to-leading logarithmic accuracy, and
provide a general expression for the leading Reggeization-breaking operator.
Our approach applies to multiparticle amplitudes in multi-Regge kinematics, and
it also implies new constraints on possible corrections to the dipole formula,
based on the Regge limit.
