We have observed transient, coherent beam combination by degenerate two-wave mixing of frequency-doubled Nd:YAG picosecond laser pulses in carbon disulfide, using a circularly polarized pump wave and a linearly polarized probe beam. The important role of beam polarization is observed, and its part in energy transfer is discussed. A theory that treats polarization effects in transient two-wave mixing is presented, applied to the carbon disulfide experiments, and found to be in excellent agreement with the data.