You've just dismantled your own argument. Your initial claim was that the defense of Sakhalin is analogous to the defense of Taiwan and low casualties by Soviet forces are indicative. You now yourself claim that Sakhalin was poorly defended due to a diplomatic factor, that clearly doesn't apply to Taiwan. Taiwan is armed to the teeth, and is actively modernizing their military to try if not keep up with China, at least to present a credible deterrent to open invasion.Japan surrendered to US, not to USSR. The main reason of the poor defense of South Sakhalin and Kurils is the Japanese belief USSR would honor the Non Aggression Treaty between USSR and Japan which Japan honored in the war by not invading USSR from the east to help Germany.