Rebel sentries were Rebel Alliance personnel who monitored incoming and departing starships and kept watch for Imperial scouts and other hazards from the top of a recon-tower near the Massassi Temple, the Rebellion's headquarters on Yavin 4. Osleo Prennert was a Rebel sentry posted during the Millennium Falcon's arrival at Yavin 4 in 0 BBY and during the moon's occupation by the Galactic Empire.