Call of Duty: Modern Warfare 2 was released in 2009 and became one of the most influential multiplayer shooters of its era, with distinct voice lines for each faction. OpFor, short for opposing force, represented the enemy team in multiplayer matches, and its soldiers used short radio callouts to announce movements, kills and objectives. Clips of those lines were later shared on soundboards and reused in gaming videos, where longtime players instantly recognise the faction sound. Their continued use comes from nostalgia for classic Modern Warfare multiplayer and the tense atmosphere the voices create.