More like 'saw what was happening' and then joined the plot to kill Hitler. A lot of Germans that hated Nazism in the army or otherwise also ended up in concentration camps or simply hung if they were found out.
That's besides the point though, if we think of CoD as purely 'war' stories, here are 5-6+ ideas just off the top of my head:
- American 'Not another Normandy story': An entire Tunisian, Sicilian, and Gothic Line (Italy) Campaign
- British: Entire Burma Campaign, The Invasion of France and Dunkirk, etc.
- German: Literally any front, no FPS-type game from this perspective (only thing I can think of terms of 'story' are RTS games). Examples of stories centered around any of these: Escaping the Korsun Pocket, Early War-through Late War (successes to late war defeat), Operation Bagration (think something like 'Crosses of Iron), a German Fallshirmjager
- Japan: Easy, holdouts such as the Fox of Saipan and others, or a Philippines campaign
- Polish: Early War invasion of Poland, survive and become a Partisan eventually linking up with Russians in late war (OR escaping Poland and joining the "Polish Armed Forces" which included anyone from deserted German Wehrmacht, Russian Evacuees, Polish Evacuees, Evacuees from France
- Finnish: Easy, the Winter War (and Continuation War).
- Russian: Surviving Operation Barbarossa and end at a major battle such as Budapest or Berlin. Other ideas would be Early War and are pushed back to Sevastopol and surrounded, captured, and escaping to become a Partisan.
And that's not even covering a quarter of possibilities. Plenty of nationalities for a character: Hungarian, French, Vichy French, Scottish, Romanian, Italian, etc. + any number of conflict areas.