Prepositional stranding (P-Stranding), which was possible only in certain types of constructions in Old English, began to be allowed more freely in the Middle English (ME) period, resulting in many new types of P-Stranding. Although many relevant studies have tried to account for the development of these new P-Stranding types, none of them or no combination of them seem to adequately explain how the new types came into being in ME and why they occurred in the order in which they occurred. In this paper, I explain why the development of new P-Stranding types in Middle English cannot be properly explained by any of the previous studies and then provide an alternative account of the advent of each new type of P-Stranding and the chronology involved on the basis of the displacement of the prepositional object from PP (DPO), a constraint on DPO (DPO), and the subject requirement (SubjR).