  SU(N_L) X SU(N_R) gauge theories are investigated as effective field theories
on D_4 branes in type IIA string theory. The classical gauge configuration is
shown to match quantitatively with a corresponding classical U(N_L) X U(N_R)
gauge theory. Quantum effects freeze the U(1) gauge factors and turn some
parameters into moduli. The SU(N_L) X SU(N_R) quantum model is realized in M
theory. Starting with an N=2 configuration (parallel NS fivebranes), the
rotation of a single NS fivebrane is considered. Generically this leads to a
complete lifting of the Coulomb moduli space. The implications of this result
to field theory and the dynamics of branes are discussed. When the initial M
fivebrane is reducible, part of the Coulomb branch may survive. Some such
situations are considered, leading to curves describing the effective gauge
couplings for N=1 models. The generalization to models with more gauge group
factors is also discussed.
