Complex sentence: The rise of Athens and Sparta during this conflict led directly to the Peloponnesian War, which saw diversification of warfare, which shifted to fighting naval battles and strategies of attrition such as blockades and sieges.
Split into simpler sentences: The rise of Athens and Sparta during this conflict led directly to the Peloponnesian War, which saw diversification of warfare. Emphasis shifted to naval battles and strategies of attrition such as blockades and sieges.