Final answer:
Alcibiades betrayed Athens twice, first fleeing to Sparta to escape treason charges, then assisting Persia after a fallout with Sparta.
Step-by-step explanation:
Alcibiades betrayed Athens twice. His reasoning for abandoning Athens and serving Sparta was to avoid trial for impiety and treason charges. In Sparta, he advised military strategy against Athens. Later, he conspired with Persia when he fell out of favor in Sparta, aiding them in exchange for support against Athens and Sparta.
After instigating the Sicilian Expedition and facing political persecution, Alcibiades fled to Sparta where he provided valuable military advice against Athens, including suggesting the fortification of Decelea and reinforcing Spartan naval strength. Following his estrangement from Sparta, he sought refuge with the Persian satrap Tissaphernes, offering intelligence and counsel against both Athens and Sparta in the hope of personal reinstatement to a position of power.