Jon was born on December 5th to Harold and Bethany Callard in Sydney, Australia. Even as a child, Jon had issues with growing up in Sydney. He always wrote in his schoolbooks that the city was 'always crowded, always moving' and that there was 'no time to do anything. There's always someone behind you moving you along'.
To avoid any damage to Jon's mental health and perceptions, his guidance councilor suggested to his parents that a move might be the best thing for Jon. His parents agreed and even had a place where they could go.
Melbourne had far less urban sprawl than Sydney did. Jon found this place rather enjoyable and grew up much better here. He often joked that his life expectancy has risen since the air is cleaner. Jon also saw propoganda for the UNSC's conquest of rebel forces in the Eta Cassiopeiae system and wanted to join up, but his parents thought against it.
Before the war erupted, Jon had the single desire of finishing his education, wanting to go into computer sciences and earn a double major in palaentology. He definetely had the marks required so there was no question as to whether he could be accepted or not. What halted all this was new and shocking rumors of antimatter devices that could devistate a whole continent. These were simply whispers on the wind, but Callard wasn't going to take the chance. Upon graduation, he immedietely put a request in for a Navy position but did not score high enough on the aptitude examination. Frustrated, he settled for the Marine Corps, knowing his life expectancy was not significantly shorter than if he became a swabbie.
Despite the fact, Jon would have taken a quick death by artillery bombardment rather than a slow and painful death from vacuum exposure. So began his journey down the road to his destiny.