  We discuss how N=1 dualities in four dimensions are geometrically realized by
wrapping D-branes about 3-cycles of Calabi-Yau threefolds. In this setup the
N=1 dualities for SU, SO and USp gauge groups with fundamental fields get
mapped to statements about the monodromy and relations among 3-cycles of
Calabi-Yau threefolds. The connection between the theory and its dual requires
passing through configurations which are T-dual to the well-known phenomenon of
decay of BPS states in N=2 field theories in four dimensions. We compare our
approach to recent works based on configurations of D-branes in the presence of
NS 5-branes and give simple classical geometric derivations of various exotic
dynamics involving D-branes ending on NS-branes.
