In his emphasis on sea power , Thucydides resembles the modern naval theorist Alfred Thayer Mahan , whose influential work The Influence of Sea Power upon History helped set in motion the naval arms race prior to World War I . The History explains that the primary cause of the Peloponnesian War was the `` growth in power of Athens , and the alarm which this inspired in Sparta '' ( 1.23.6 ) .
The History explains that the cause of the Peloponnesian War was the `` growth in power of Athens , and the alarm which this inspired in Sparta '' ( 1.23.6 ) .