  We investigate interactions between branes of various dimensions, both
charged and uncharged, in three non-supersymmetric string models. These include
the $USp(32)$ and $U(32)$ orientifold projections of the type IIB and type $0$B
strings, as well as the $SO(16) \times SO(16)$ projection of the exceptional
heterotic string. The resulting ten-dimensional spectra are free of tachyons,
and the combinations of branes that they contain give rise to rich and varied
dynamics. We compute static potentials for parallel stacks of branes in three
complementary regimes: the probe regime, in which one of the two stacks is
parametrically heavier than the other, the string-amplitude regime, in which
both stacks are light, and the holographic regime. Whenever comparisons are
possible, we find qualitative agreement despite the absence of supersymmetry.
For charged branes, our analysis reveals that the Weak Gravity Conjecture is
satisfied in a novel way via a renormalization of the effective
charge-to-tension ratio.
