We investigate efficient power allocation schemes for retransmission protocols over wireless fading channels. In prior work, we considered this problem for i.i.d. fading with known channel statistics. Here, we consider models for channels with memory and adaptive power control algorithms for channels with unknown statistics. In the case of channels with memory we consider simplified power policies for Go-back-N protocols via Markovian modeling, which take into account the underlying window dynamics. These policies are observed to perform close to a more complicated Dynamic Programming (DP) solution. We then give an adaptive power control algorithm for protocols in which window dynamics can be ignored. The protocol is based on Lyapunov drift analysis and is shown to approach that of an optimal policy.