Equivalence of Geometric Engineering and Hanany-Witten

We show the equivalence of three different realisations of gauge theory in string theory. These are the Hanany-Witten brane constructions, the use of branes as probes and geometric engineering. We illustrate the equivalence via T- and S-dualities with the simplest non-trivial examples in four dimensions: N = 2 SYM with gauge groups SU(N_1) x SU(N_2) x .....