"Hey, wouldn't it be cool if President Roosevelt sent a bunch of investigators to stop Hitler from summoning Cthulhu?" is a thing a gamer might think when they were fourteen. Then you learn a little about World War 2 and which side, if he had lived that long, Lovecraft would undoubtedly have sided with, and suddenly the bloom is off the rose. The concept of a mad Nazi sorcerer is frankly, stupid and a waste of everyone's time. They didn't need sorcery to be horrible. Sorcery is fictional and Nazi mass murders were real. What would they have done with sorcery that they didn't do with their own determination? Spread their evil further, win maybe? But that doesn't make them a different kind of evil; they don't become more horrific if you give them tentacle monster shock troops, they just become more successful at spreading the horror they launched. The more I learned about World War 2, the less I liked attempts to shoehorn the Cthulhu Mythos into it. Let's not even get to the Victorian anxieties that bubbled just beneath the surface of Mythos writings; suffice to say the Allied armies (racially diverse, eventually even racially integrated!) would not be the good guys in a Lovecraftian Mythos tale. Thus, for many years I put down the recurring idea of a WW2 Mythos game. I may have even been mean about it once or twice!
So when I saw World War Cthulhu: Darkest Hour, I was fairly decidedly disinterested, even though it was Cubicle 7 and I normally quite like Cubicle 7 games. Nevertheless I decided to give it a look and I'm very glad that I did. WWC has a very different attitude towards how to design a Call of Cthulhu scenario in World War 2 which transforms the war from a shorthand 5th grader's scribble of bad Nazis seeking forbidden knowledge to a setting that presents tremendous challenges to investigators seeking to achieve military and potentially occult goals at the same time.
In your typical Call of Cthulhu scenario, investigators receive a weird invitation or see a bizarre story in the newspaper that is in their professional field. They gather up because they know weird shit might be going down and start digging into it. Importantly, in Call of Cthulhu scenarios, you can lose. It is quite possible to miss clues, miss events on a timeline, misinterpret the clues and go to the wrong place, and you never solve the mystery, and then you see another horrible newspaper article and you FEEL AFRAID at the unknown horror that you almost spotted, and lose Sanity. This makes a typical Call of Cthulhu scenario a self-contained episode. However, in WWC, a different methodology is at work.
In WWC, you identify a location and determine what's going on with the war as an environment that the investigation takes place in. The sample campaign (more on this below) is a small town in Vichy France near a mysterious wood and a copper mine the Nazis really want to keep open. Then you create the occult threat and what might draw the investigators to the area. This approach guarantees you're not going to have your team of rowdy investigators winning the war singlehandedly, and also guarantees that they will have to thread some very difficult needles. In a (separately published) scenario, for example, there's a mysterious occult plague in a town controlled by Italian fascists. They believe (and spread the word) that they are being targeted by an Allied biological weapon of some kind. But it isn't; it's a MONSTER. You can definitely see how investigators who come into that situation will have to walk a tightrope between the danger of the Mythos and the danger imposed by the war. And when there's a plague monster around, maybe calling in an artillery strike is the worst thing to do. ("Are those spores or smoke?")
WWC asks not that you treat WW2 as a pulp setting, but instead asks that you treat it as real, with real stakes. And that, to me, is the innovation that makes it work where other WW2 Cthulhu scenarios have failed.
The sample campaign (which I'm going to be running soon!) is a great example. The characters are Special Operations Executive agents parachuting into the Vichy France countryside in April 1941 (seven months before the Americans even get into the action!) with the mission of putting together an intelligence network in the countryside, and finding out what happened to the investigator who disappeared before the Nazi invasion. He was looking into a cult, naturally, but the investigators can't just pop in to a Vichy village and start asking questions and avoiding attention because then they'll be pegged as spies immediately and killed by the Gestapo, and the cult will be about its evil business unimpeded.
And there are questions about how much to trust the Resistance that's helping you...or even if you trust them, how much to involve them? They have different goals and restrictions, and they may or may not know about or believe in the occult problems the investigators have to deal with. If a monster's going to eat a bunch of people, you have to balance whether you want a suave lady shooting a Sten while smoking a cigarette standing next to you, or whether it would be better if she didn't have her arm eaten and nerve broken so she would have both those things to fight the Hun.
All in all, World War Cthulhu is a tremendous effort, works really well, and the sample campaign gives a very solid example as to how to design a WWC scenario. This game completely rehabilitates the idea of the WW2 Mythos scenario and breathes new life into it with the relentless focus on the war as environment instead of the war as event.
If I had to suggest a way to improve this effort, I would mention there are several typographical errors (the names of characters in the sample campaign aren't always spelled the same way, etc.) and I would really hammer out several different campaign structures other than the SOE structure that's presented. All in all, however, this is an exceptionally solid work that accomplishes something many have attempted but rarely successfully. It's definitely worth your time.