This document discusses the balance of power system in 19th century Europe and the lead up to World War 1. It describes how Europe had a multipolar system from 1815-1914 characterized by shifting alliances among 5 or 6 great powers. This period saw shifting alliances and the rise of Germany as a new great power. By 1907-1914 the system became rigidly divided into opposing alliance blocs. The document analyzes this system using realist and constructivist perspectives, discussing how nationalism and new norms challenged the balance of power but realism's security dilemma remained. It suggests World War 1 resulted from this rigid alliance system and the security dilemma as countries mobilized in response to perceived threats.