The mechanism of crack arrest in a composite with long fibers is analyzed by using the inclusion method. Fibers suppress a crack opening by a bridging action. Sliding along the matrix-fiber interface results in energy dissipation. The bridging action reduces the energy release rate G for the crack extension. The energy dissipation due to sliding and interfacial debonding produces additional resistances ΔGS and ΔGd to the crack extension. G, ΔGS and ΔGd are calculated in terms of external stresses, frictional stresses, the size of a crack, the debonding length, the interface surface energy and the volume fraction of the fibers.