The semiclassical interaction of a two-level atom with a singlemode ®eld, taking into account the atomic reaction onto the ®eld, is considered. Analytical expressions for the ®eld and atomic dynamics are found. An expansion of this solution in terms of the inverse of the ®eld intensity is performed. To zeroth order, the classical Rabi solution is recovered, while ®rst-order corrections give rise to a slow modulation of the atomic dipole, in agreement with a fully quantum model. The evolution of the atomic dipole is studied in the framework of the reduced Q function, both in the semiclassical and quantum regimes. PACS 42.50.Dv ± 03.65.-w.