This paper aims to reconstruct the developmental processes of /r/-sandhi in the history of English. Two opposing views on the inception and subsequent diachronic development of /r/-sandhi (/r/-deletion and /r/-insertion) are critically assessed in terms of both diverse assumptions employed in theoretical accounts of /r/-sandhi in Present-Day English (PDE) and typological patterns of /r/-sandhi among rhotic and nonrhotic dialects. Based on implications derived from each view, it is argued that /r/-deletion should be regarded as the legitimate trigger of /r/-sandhi and that Intrusive-/r/ is a derivative phenomenon of Linking-/r/. It is also demonstrated that hyper-rhoticity, both at present and in the past, bears little connection with the diachrony of /r/-sandhi. In addition, the diachrony of /r/-sandhi as proposed in this paper crucially depends on and, thus, supports the synchronic coexistence of deletion and insertion.