  We propose that the Ultra-Diffuse Galaxy (UDG) population represents a set of
satellite galaxies born in $\sim10^{10}-10^{11}$ M$_\odot$ halos, similar to
field dwarfs, which suffer a dramatic reduction in surface brightness due to
tidal stripping and heating. This scenario is observationally motivated by the
radial alignment of UDGs in Coma as well as the significant dependence of UDG
abundance on cluster mass. As a test of this formation scenario, we apply a
semi-analytic model describing the change in stellar mass and half-light radius
of dwarf satellites, occupying either cored or cuspy halos, to cluster subhalos
in the Illustris-dark simulation. Key to this model are results from
simulations which indicate that galaxies in cored dark-matter halos expand
significantly in response to tidal stripping and heating, whereas galaxies in
cuspy halos experience limited size evolution. Our analysis indicates that a
population of tidally-stripped dwarf galaxies, residing in cored halos (like
those hosting low-surface brightness field dwarfs), is able to reproduce the
observed sizes and stellar masses of UDGs in clusters remarkably well.
