Plaid Cymru’s history can most usefully be divided into three periods: its origin under the leadership of Saunders Lewis until his resignation in 1939; the period of gradual transformation under the leadership of Gwyfor Evans from 1945 to 1980, and the emergence of a modernist platform in the 1980s and 1990s. For the purposes of this volume, the more recent period is most significant, yet certain foundations were laid in the early periods which still bear on current problems and therefore deserve a brief introduction.