    ‘Sentence + When .did the .age of imperialism  begin?    Sentence 2: Although: imperialist practices have  existed for thousands: of years, the term "Age of  Imperialism” generally tefers to the activities. of  European powers from the early 18th century:  through to: the middle .of the 20th century, for  ‘example, the "The Great Game”. in Persian lands,  the. "Scramble for. Africa” and ‘the "Open Door.  Policy” in Chin:    