A one-dimensional array of pulse--coupled integrate--and--fire neurons, each filtering input through an idealised passive dendritic cable, is used to model the nonlinear behaviour induced by axo-dendritic interactions in neural populations. The relative firing phase of the neurons in the array is derived in the weak-coupling regime. It is shown that for long-range excitatory coupling the phases can undergo a bifurcation from a synchronous state to a state of travelling oscillatory waves. We establish the possible role of dendritic structure in the desynchronization of cortical oscillations.