Last days of the Old Republic

Darth Vader, Dark Lord of the Sith, helped the Emperor hunt down and exterminate the Jedi Knights during the last days of the Old Republic and the opening moments of the Empire. Later, he was sent to help Governor Tarkin develop the original Death Star battle station. Once the Rebellion demonstrated that it posed a significant threat to the New Order, Lord Vader was put in charge of the Imperial fleet assigned to find and destroy the Alliance leaders.