Answer: Although modern Western ideas about romantic love owe a certain amount to the classical Greek and Roman past, they were filtered through the very different culture of the European Middle Ages. One can trace the concepts which dominated Western thinking until recently to the mid-12th Century. Before that time, European literature rarely mentions love, and women seldom figure prominently. After that time, within a decade or two, all has changed. Passionate love stories replace epic combat tales and women are exalted to almost god-like status. Simultaneously, the Virgin Mary becomes much more prominent in Catholic devotions, and emotionalism is rampant in religion.
The pioneers of this shift in sensibility seem to have been the troubadours, the poets of Provence (now Southern France). Provençal is a language related to French, Italian and Spanish, and seems to have facilitated the flow of ideas across the often ill-defined borders of 12th-Century Europe. It has often been speculated that Arabic poetry may have influenced their work by way of Moorish Spain. Although this seems likely, it is difficult to confirm.
Explanation: Once the basic themes are laid down by the troubadours, they are imitated by the French trouvères, the German Minnesingers (love poets) and others. Thus, even though the disastrous 13th-Century Albigensian crusade put an end of the golden age of the troubadours, many of their ideas and themes persisted in European literature for centuries afterward.