The Plague of Athens in 430 BCE greatly weakened Athens during the Peloponnesian War.
The event that greatly weakened Athens starting in 430 BCE was the outbreak of the Plague of Athens during the Peloponnesian War. The plague, attributed to Salmonella enterica serovar Typhi, caused significant casualties, with an estimated 25% of the population succumbing to the disease. This catastrophic event severely impaired Athens' military strength and overall dominance.
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