Theory of hadronic B decays

I give an overview of the theory of hadronic nonleptonic B decays into two light mesons. Using the soft-collinear effective theory (SCET), a factorization theorem for these processes has been proven to leading order in 1/mb. The phenomenological implications of this factorization relation for B-> \pi\pi decays are discussed, together with the prospects for determining the weak phase \alpha(\phi_2) from these modes.