the Germans started colonizing Eastern Europe beyond the Empire, into Prussia and Silesia. In the mid 13th century, the "Pax Mongolica" re-invigorated the land-based trade routes between China and West Asia that had fallen dormant in the 9th and 10th centuries. Following the Mongol incursion into Europe in 1241, the Pope and some European rulers sent clerics as emissaries and/or missionaries to the Mongol court; these included William of Rubruck, Giovanni da Pian del Carpini, Andrew of Longjumeau, Odoric of Pordenone, Giovanni de Marignolli, Giovanni di Monte Corvino, and other travelers such as Niccolò da Conti. While the accounts of Carpini et al were written in Latin as letters to their sponsors, the account of the later Italian traveller Marco Polo, who followed his father and uncle as far as China, was written first in French c.1300 and later in other popular languages, making it relatively accessible to larger groups of Europeans. Science After the collapse of the Western Roman Empire, Western Europe had entered the Middle Ages with great difficulties. Apart from depopulation and other factors, most classical scientific treatises of classical antiquity, written in Greek or Latin, had become unavailable or lost entirely. Philosophical and scientific teaching of the Early Middle Ages was based upon the few Latin translations and commentaries on ancient Greek scientific and philosophical texts that remained in the Latin West, the study of which remained at minimal levels. Only the Christian church maintained copies of these written works, and they were periodically replaced and distributed to other churches. This scenario changed during the renaissance of the 12th century. For several centuries, popes had been sending clerics to the various kings of Europe. Kings of Europe were typically illiterate. Literate clerics would be specialists of some subject or other, such as music, medicine or history etc., otherwise known as Roman cohors amicorum, the root of the Italian word corte 'court'. As such, these clerics would become part of a king's retinue or court, educating the king and his children, paid for by the pope, whilst facilitating the spread of knowledge into the Middle Ages. The church maintained classic scriptures in scrolls and books in numerous scriptoria across Europe, thus preserving the classic knowledge and allowing access to this important information to the European kings. In return, kings were encouraged to build monasteries that would act as orphanages, hospitals and schools, benefiting societies and eventually smoothing