As the introduction noted, Halford Mackinder defined his era as one that had begun, approximately, with the voyages of Columbus and was, he believed, coming to a close in his own day. In the period between the Renaissance and Mackinder’s own time, European maps of the world were progressively filled in as the geographical knowledge of their makers increased.43 Although Mackinder himself was a geographer, he derived little satisfaction from this accomplishment because he worried that with the closing of the Columbian Epoch, the effectiveness of British sea power as a strategic tool was also waning. This, he surmised, could have disastrous consequences both for the British Empire and Western civilization in general. Mackinder foresaw that in the new “postColumbian age,” the West would have to contend with a worldwide “closed political system,” a condition that bore some resemblance to the age before the Columbian Epoch, when “mediaeval Christendom was pent up in a narrow region” and acutely threatened from outside. In the Columbian Epoch, Western civilization had the good fortune to break out of its trap by sea and enjoy a strategic golden age in which it expanded its influence explosively.44 However, there would be no escape from the new closed system.