Bales had pleaded guilty to all 17 counts during his court-martial hearing in July, which eliminated the possibility of a death sentence.
At the time of the shootings, the 38-year-old Iraq war veteran had been in Afghanistan since December on his fourth combat tour in 10 years.
However, military prosecutors built their case on chilling eyewitness testimony, which described a cold, calculating Bales move from home to home in the Afghan village near his base in Kandahar, shooting men, women and children.
Bales' rampage reportedly included two trips to the surrounding villages in southern Afghanistan, returning to his base between shootings to retrieve more ammunition.
The incident prompted those inside the Pentagon and on Capitol Hill to revisit the issue of PTSD and the overall state of the U.S. military, whose members have been engaged in combat operations in Iraq and Afghanistan for more than a decade.
Shortly after the shootings, Sen. Patty Murray (D-Wash.) pressed Army officials on how pervasive the cases of PTSD were among U.S. troops returning home from war.
That said, the DOD claims "the science has not been able to identify" any clear links between PTSD, TBI and violent incidents like the shootings Bales was convicted of, according to Pentagon officials.
Bales's verdict came on the same day a separate military court at Ft. Hood, Texas convicted Army Maj. Nidal Hasan on charges that he killed 13 people and injured 32 others in a 2009 shooting at the military base.
Hasan opened fire on the U.S. troops stationed at Ft. Hood as they were preparing to deploy to Afghanistan.
Hasan was also scheduled to head to Afghanistan with his Army medical unit before going on the shooting rampage.
During the ensuing investigation, Hasan reportedly told Army officials the attack was designed to protect Taliban fighters who would have to fight the deploying U.S. troops once they arrived in country.
Hasan attempted to use that argument as part of his defense, but Army Judge Col. Tara Osborne refused to allow it into the trial.