Complex sentence: He studied History at Bonn and at Berlin, where his teachers included von Ranke, Böckh and Karl Lachmann, before embarking on a career as a secondary school teacher.
Split into simpler sentences: He studied History at Bonn and at Berlin, where his teachers included von Ranke, Böckh and Karl Lachmann. On leaving univesity he embarked on a career as a secondary school teacher.