In Vulgar Latin, the original diphthong first began to be pronounced as a simple long vowel . Then, the plosive before front vowels began, due to palatalization, to be pronounced as an affricate, hence renderings like in Italian and in German regional pronunciations of Latin, as well as the title of Tsar. With the evolution of the Romance languages, the affricate became a fricative (thus, and the like) in many regional pronunciations, including the French one, from which the modern English pronunciation is derived.
In Vulgar Latin, the original diphthong first began to be pronounced as a simple long vowel . Then, the plosive before front vowels began, due to palatalization, to be pronounced as an affricate, hence renderings like in Italian and in German regional pronunciations of Latin, as well as the title of Tsar. With the evolution of the Romance languages, the affricate became a fricative (thus and the like) in many regional pronunciations, including the French one, from which the modern English pronunciation is derived.