This book provides a detailed introduction to the development of the German language from the earliest reconstructible prehistory to the present day. A key to understanding how any human language works is understanding how that language developed over time. German speakers, as well as language learners and teachers are often puzzled by many questions about the German language: How did German come to have so many different dialects and close linguistic cousins like Dutch and Plattdeutsch? Why does German have 'umlaut' vowels and why do they play so many different roles in the grammar (noun plurals and subjunctive verbs, among many more)? Why are noun plurals so complicated (-e, -en, -er, umlaut, -s or nothing at all)? Are there reasons for the different gender markings in the language (die Woche versus das Auge)? Are dialects dying out today? Does English, with all the words it loans to German, pose a threat to the language? Full, satisfying answers to many of these questions are emerging in current research and this book presents, in an accessible manner, a concise linguistic introduction to the history of German as specialists understand it today. The book is supported by a companion website and is suitable for language learners and teachers and students of linguistics, from undergraduate level upwards.