In Crusader kings I am playing as Pomerania and as a matter of making my game more interesting I decided at the start to not convert to Catholicism and stay as a Slavic pagan until the end of the game. I have managed to cut Great Moravia down to size. However in 10th century HRE formed out of East Francia and controls far more than its historic region - they control Italy, South France (Occitania), Germany and Lotharingia. So their manpower is about 150k, mine currently sits around 45k-55k. None of the larger neighbours of mine are of Slavic religion (Suomenusko to the east, the rest Catholic), so no feasible alliance marriages outside the realm. I control almost exactly the area of the in-game dejure Wendish Empire (although I have not formed it). Also, I have reformed the Slavic faith.
In this context, HRE declared a holy war on me for one of the duchies in the west. With the difference in manpower and their humongous stacks, I stand little chance of victory in the conflict. Short of accepting the conversion to the Catholic faith (which ends the holy war), what are my short and long term options at keeping the HRE at bay?