Sledgehammer Games decided to rise to the challenge by promising fans that its latest instalment in the Call of Duty franchise would not 'shy away' from history. The scale of the Nazis' killing machine is hard to comprehend more than 70 years on, so how do you replicate those horrors in a visual medium designed for entertainment? More than six million Jews and three million others were rounded up, dehumanised and shoved into cattle cars before being locked up in one of 40,000 concentration camps, where they were experimented on, shot and gassed. The end of the Second World War unearthed the truth of the darkest days for humanity. WARNING: This piece contains major spoilers for Call of Duty: WW2's campaign.