  We investigate the transmutation of D-branes into Abelian magnetic
backgrounds on the world-volume of higher-dimensional branes, within the
framework of global models with compact internal dimensions. The phenomenon,
T-dual to brane recombination in the intersecting-brane picture, shares some
similarities to inverse small-instanton transitions in non-compact spaces,
though in this case the Abelian magnetic background is a consequence of the
compactness of the internal manifold, and is not ascribed to a zero-size
non-Abelian instanton growing to maximal size. We provide details of the
transition in various supersymmetric orientifolds and non-supersymmetric
tachyon-free vacua with Brane Supersymmetry Breaking, both from brane
recombination and from a field theory Higgs mechanism viewpoints.
