German expansion into Slavic lands begins in the 12th-13th-century (see Drang Nach Osten). The concept of Drang Nach Osten was a core element of German nationalism and a major element of Nazi ideology. However, the German involvement in the seizure of overseas territories was negligible until the end of the 19th century. Prussia unified the other states into the second German Empire in 1871. Its Chancellor, Otto von Bismarck (1862–90), long opposed colonial acquisitions, arguing that the burden of obtaining, maintaining, and defending such possessions would outweigh any potential benefits. He felt that colonies did not pay for themselves, that the German bureaucratic system would not work well in the tropics and the diplomatic disputes over colonies would distract Germany from its central interest, Europe itself.