Peter wrote this letter around A.D. 60. It is clear from 1:1,2 he is addressing redeemed Jews in the diaspora. The theme running through the book is preparation for victory over suffering. A quick search reveals Peter uses a form of the word suffering sixteen times. It is a keyword in his epistle.
While written to Jewish believers, we who are non-Jews can see what our conduct should be when we encounter suffering, and we can see what our Christian service can be in light of the coming of the Chief Shepherd (5:1-14).