The behavior of simple oxides bombarded by ions of noble gases is widely documented in connection with studies involving electron and ion spectroscopies and transmission electron microscopy, and also with ion-beam assisted layer deposition or removal. In the present work a new approach to the problem of beam-oxide interaction involving a complex oxide possessing two cations is outlined. Complex oxides provide an unusual opportunity to gain insight into beam-oxide interaction for the simple reason that the two or more types of cation compete in forming bonds. Specifically, the effects of bombardments by 1-4 keV argon and nitrogen ions are compared for r.f. sputter deposited homogeneous, amorphous Cr-Si-O layers. It is established that (a) Ar+ bombardment causes loss of O with the simultaneous formation of Si0 states and Si-Cr bonds, (b) N2+ bombardment causes still further loss of O as we have shown for a variety of simple oxides, and (c) at the same time N2+ bombardment diminishes the Si-Si or Si-Cr bonds with indication of partial replacement by Si-N and to a lesser extent by Cr-N bonds. These results can be explained by the prominent role of thermodynamic driving forces.