  The first, self-consistent calculations are presented of the cosmological,
H2-dissociating UV background produced during the epoch of reionization by the
sources of reionization. Large-scale radiative transfer simulations of
reionization trace the impact of all the ionizing starlight on the IGM from all
the sources in our simulation volume down to dwarf galaxies of mass ~10^8 Msun,
identified by very high-resolution N-body simulations, including the
self-regulating effect of IGM photoheating on dwarf galaxy formation. The UV
continuum emitted below 13.6 eV by each source is then transferred through the
same IGM, attenuated by atomic H Lyman series resonance lines, to predict the
evolution of the inhomogeneous radiation background in the Lyman-Werner bands
of H2 between 11 and 13.6 eV. On average, the intensity of this Lyman-Werner
background is found to rise to the threshold level at which dissociation
suppresses H2 cooling and star formation inside minihalos, long before
reionization is complete. Spatial variations in the Lyman-Werner background are
found which result from the clustering of sources associated with large-scale
structure formation, such that intensity fluctuations correlate with matter
density fluctuations. As a result, the Lyman-Werner background rises to the
threshold level for H2 suppression earlier in the vicinity of the reionization
sources and their H II regions.
