<P> Seeking revenge after his wife Mary was killed by the demon Azazel, John Winchester became a hunter and raised his two sons to fight the supernatural . John disappears early in Supernatural, and the first season revolves primarily around Sam and Dean trying to find him . Morgan was also filming episodes of Grey's Anatomy while the first season of Supernatural was under production, and future appearances of the character were hindered by his busy schedule . While Morgan's portrayal has been praised, fans and critics were generally frustrated at the character for keeping so many secrets . </P> <P> The father of series protagonists Sam and Dean Winchester, John Winchester first appears in the pilot episode of the series, but plot devices such as flashbacks and time travel detail his background in later seasons . Apparently abandoned by his father at a young age--his father actually died while serving a secret order known as the Men of Letters--John Winchester grew up hating the man . John left high school to join the Marine Corps, eventually attaining the rank of corporal and receiving many medals for his service in Vietnam . After leaving the service, he found a job as a mechanic, and fell in love with Mary Campbell . </P> <P> In the fourth season episode "In the Beginning," Dean is sent back through time by the angel Castiel . Dean meets his parents' former selves, and ends up convincing John to buy the 67 Chevy Impala that he eventually inherits . Dean later watches John being killed by Azazel, though the demon then resurrects him in exchange for Mary's permission to enter her house in ten years . When the angel Anna Milton travels back in time in the fifth season episode "The Song Remains the Same" to prevent the births of Sam and Dean, John agrees to serve as a temporary vessel for the archangel Michael to stop her . Michael subsequently kills Anna and erases John and Mary's memories of the incident . </P> <P> Azazel later uses his pact with Mary to enter their home in the pilot episode, and ultimately kills her . The second season episode "All Hell Breaks Loose, Part One" reveals that she had witnessed the demon secretly feeding his blood to Sam . John investigated the incident and learned of the existence of the supernatural . His desire to find and kill Azazel led him to become a hunter of supernatural creatures . He took his sons with him during his travels, but often left them alone in motels for long periods of time during his hunts, leaving Dean with instructions to "shoot first and ask questions later" while watching over Sam . </P>

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