Johann Gustav Droysen (1808–84) belonged to a German school of historical thought influenced by Hegel, which emphasised the role of great individuals in history. A pupil of August Boeckh, his own famous students included Jacob Burckhardt. He was noted for his thorough and painstaking use of source materials, and his history of Alexander the Great (1833) remained the standard work on the subject for many years. In 1836–43 Droysen published this pioneering two-volume study of the centuries after Alexander's death, and it was Droysen who coined the term Hellenism to refer to this period. Volume 1 focuses on Alexander's successors and covers the period 323–278 BCE, from Alexander's death to the campaigns of Demetrios Poliorcetes, ending with the invasion of Macedonia by the Gauls. Volume 2 describes the formation of the Hellenistic states between 280 and 221 BCE and the associated power struggles in the Mediterranean region.