World at War is based on real events but naturally adds its own Call of Duty spin while Vanguard is largely a work of fiction. Funny enough, the two do share one point in common: A Russian sniper. Vanguard's Polina picks up her father's old rifle after he's killed by Nazis in the bombing of Stalingrad.
Modern Warfare II introduces several design improvements and changes to the series gameplay, such as advanced AI systems in the campaign and co-op modes, water physics, swimming mechanics, and an overhauled vehicle system.