Between September 1992 and August 1994, Galic commanded the Romanija Corps of the Bosnian Serb army that laid siege to Sarajevo and killed hundreds of Muslim civilians in a campaign of shelling and sniping.
During the 44-month siege of the Bosnian capital 10,500 people were killed by sniper and shell fire.
When he was originally convicted in 2003 of four crimes against humanity, including murder and inhumane acts and a war crime, the trial judges said Galic's forces had deliberately snipped at and shelled Muslim civilians.
The judges said: "They were attacked while attending funerals, while in ambulances, trams, and buses, and while cycling. They were attacked while tending gardens, or shopping in markets, or clearing rubbish in the city. Children were targeted while playing or walking in the streets."
Galic reported directly to one of the tribunal's most-wanted suspects, Ratko Mladic, the Bosnian Serb military leader, and was the first person convicted by the tribunal of the war crime of using acts of violence to spread terror among a civilian population.
In one attack in 1994, a mortar shell killed about 60 people and injured more than 100 at a market in downtown Sarajevo. The trial judges ruled that the shell was fired by Galic's troops.
The appeals court rejected all 19 of Galic's grounds for appeal, including challenges to the court's jurisdiction and claims that he did not know his forces were involved in illegal sniping and that his sentence was too high.
The decision to increase his sentence was reached by a majority in the five-judge appeal chamber.