The US soldier who was convicted of mass murdering 16 Afghan villagers while on deployment in 2012, revealed he was "consumed by war" and antipathy for anyone who wasn't American.

In a letter sent late last year to Lt. Gen. Stephen Lanza, Staff Sgt. Robert Bales begged the Army to overturn or reduce his August 2013 sentence of life without parole, writing that he "would do anything not to be the bad guy."

"I planted war and hate for the better part of 10 years and harvested violence," he wrote. "After being in prison two years, I understand that what I thought was normal was the farthest thing from being normal."

The letter, obtained by Seattle's News Tribune newspaper through a FOIA request, failed to sway Lanza, who refused to modify the plea deal Bales took in order to escape the death penalty. The case will now be referred to the Army Court of Criminal Appeal, a spokesman said Friday.

Bales, 41, an Ohio native and father of two, shot a total of 22 people, including 17 women and children, in two nighttime raids on two villages in Afghanistan's Kandahar Province in March 2012. He set some of the bodies on fire. The widespread outrage in the wake of the killings forced the US Army to temporarily suspend operations in the region.

In the letter, Bales said that his PTSD triggered heavy drinking and use of sleeping pills and steroids, which in turn contributed to his paranoia and the innate rage he felt towards locals. Over the course of three earlier deployments in Iraq, he grew to be suspicious and hateful of "everyone who isn't American," he wrote.

Financial stress and marital problems also added to the stress.

"I became callous to them even being human; they were all enemy. Guilt and fear are with you day and night. Over time your experiences solidify your prejudice," he added.

Yet Bales also acknowledged there is no reason for his actions, saying "I have come to understand there isn't a why; there is only pain."

Since his imprisonment at the Army prison at Fort Leavenworth, Kansas, Bales has reportedly been baptized and become focused on Christianity, he wrote. He has also been working toward completing a bachelor's degree and learning how to be a barber.

Watch the VICE News documentary: "Deported War Veterans of America.**"**