A theory for sea scatter at large incident angles (0>30¿) is developed by using a two-scale toughness model. The small-scale waves are assumed to satisfy the small perturbation assumptions, and the large-scale waves to satisfy the physical optics approximations. Measured sea surface slope density and sea spectra reported by oceanographers are incorporated into the theory to explain effects of incident angle, polarization, frequency, wind speed, and anisotropic characteristics of the sea surface. It is observed that the increase of the backscattering coefficients with the wind is due primarily to the growth of the sea spectrum and, to a lesser extent, to the interaction between the two scales of roughness. This interaction effect is also the cause of the shift of the minimum of the scattering coefficient around the crosswind direction toward the downwind direction. The difference between the upwind and crosswind observations is the result of the anisotropic characteristics in the sea spectrum generated by the difference between the upwind and crosswind slope variances. The difference between the upwind and downwind observations is the consequence of the skewness in he slope probability density function of the large-scale waves defined with respect to the plane perpendicular to the look direction. Comparison with some experimental data shows satisfactory agreement.