Does the Quran encourage violence against the disbelievers (non-Muslims)?
The historical context is that this Quran verse was revealed at the Battle of Badr, a battle in which the pagans of Makkah traveled over 200 miles to destroy the Muslims of Madinah. The Pagans of Makkah had an army of about 1000 while the Muslims were only 300 followers. Muhammad and his followers had suffered severe persecutions and torture for 13 years in the city of Makkah. Having fled from Makkah to the safety of Madinah, they found that they were once again threatened.
It is obvious from historical and textual context therefore that this Quran verse does not promote the killing of innocents.