Sig Handsone is brilliant. His exemplary tactical sense leads him to make intelligent plans and decisions. Ironically, that's exactly what got him thrown in prison.
Sig joined the military at a young age, and would have excelled, if not for his tendency to question orders. Every time a superior officer made a decision, Sig pointed out the flaws and offered an alternative. He never gave up this practice, even though the officers rarely changed their minds. Sig was often punished for his outbursts, and he was never promoted.
One fateful day, Sig's company was ordered to march straight through a remote mountain pass in enemy territory. Sig pointed out that they would be under prime conditions for an ambush, but his commander refused to reconsider. Sig's fellow soldiers agreed with his reasoning, however, and likewise refused to obey the order. Sig was charged with inciting a mutiny and led away in chains. The company marched on, and most of the soldiers were killed.
Prison was hard on Sig. Rumors were spread about him, and they were sufficiently twisted until Sig was blamed for his company's death. The other prisoners shunned or abused him. One of them shattered his leg, which is why he now walks with a limp.
Sig, deeply embittered even at his young age, welcomes the opportunity to lead on the island. However, he is abrasive, often unwilling to compromise, and he shouts orders with undue authority. Even when he's correct, he fails to command respect.