Achtung! Cthulhu is a horror fiction role-playing game based on H. P. Lovecraft's Cthulhu Mythos set during World War II. The game is published by Modiphius Entertainment. The game was first released in 2012, and seven editions have been published to date. The game is compatible with both the sixth edition of Call of Cthulhu and the Savage Worlds game system.
The game takes place in the world of the Cthulhu Mythos, during World War II. One can find himself (or herself) right in the middle of a battle in a city, in the arid deserts of North Africa, a steaming jungle in the Pacific Ocean, the freezing cold of Russia during the winter, in an air battle, or in a naval battle. On the other hand, you can be part of an expedition to the Antarctica, some forgotten island, a lost city in the desert, or some other location searching for ancient technology or occult artifacts. You can be playing a game of espionage and counter-espionage, investigating a murder or mystery, as part of a partisan unit, or some other activity behind enemy lines or in home territory. It's a setting that combines total war, espionage, mystery, adventure, detective work, small unit level combat, magic, alien technology, super science, and of course entities and races of the Mythos.
It is a multi-sided conflict, which is mostly in the shadows. The German Mythos factions battle their counterparts among the Allied powers (Soviet Union, Great Britain, and the United States) in Europe, Africa, and elsewhere. The Japanese Mythos faction battles its Allied counterparts in the Far East and Pacific Ocean. Within the Nazi Empire of the Germans, the Cult of the Black Sun battles with its rival the Nachtwölfe. In the Soviet Union, a similar conflict occurs between the Institute 21 and Otdel MI.
- Cult of the Black Sun: The Die schwarze Sonne (the Black Sun) was founded by the sorcerer Reinhardt Weissler. Black Sun is a name that strikes fear among the Nazis, a name which is feared by even the Einsatzgruppe death squads. Usually they operate using a scientific or academic facade, even among the German military. It's members are feared and mistrusted by those in the Wehrmacht. Black Sun practices the darkest and most twisted of crafts alongside their brothers in the SS, moving behind the scenes of the Nazi empire with impunity. The cult is a sorcerer heavy society, whose sorcerers call on terrible gods and encourage casualties on their side to please their gods. Their ultimate goal is to bring to the material realm (Earth), the Black Sun from the Dreamlands. Weissler is under the influence of Nyarlathotep.
- Nachtwölfe: Was founded by a former member of the Black Sun, Mina Wolff who wanted to exploit the ancient technology that Black Sun expeditions had discovered but whose leader the sorcerer Weissler was not interested in. She gained the favor of the Fuhrer with a demonstration, and her organization was born. Dedicated to the exploitation of lost technology and using it to create ever more powerful and fearsome machines of war.
- Cthulhu Cult: Which has its roots in the Pacific Ocean. It consists of Deep Ones and their human allies, who have been seduced or bribed with promises of wealth and/or power. Their ultimate objective is to free Cthulhu. In the meantime they increase their numbers by breeding with humans (willingly or unwillingly) and spread their influence. Often working with the Cthulhu Cults are the Star-Spawn that still remain on Earth. They also are trying to free the Sons of Cthulhu (Ythogtha, Ghatanothoa, and Zoth-Ommog), all of whom are imprisoned in the Pacific Ocean.
- Nyarlathotep: It has cults across the world, each of which is dedicated to a different incarnation of the god. The main cults are in China, Australia, Kenya, Egypt, Mexico, and in the United States.
- Thousand Sons: An organization founded by the ancient race, the Naga. Their last great city was Hsatth, in Korea where they retreated to and sealed themselves in the underground city. A dozen Naga (the last remaining ones on Earth) rule over the Serpent People. They have taken control of the Matsumi Mining Company (the most powerful zaibatsu). Afterwards they infiltrated the Japanese Army and then created the "Thousand Sons" a group within the military to influence Japanese policy and operations. It's influence has spread to the Japanese Navy. Unlike the human followers of the Great Old Ones (Black Sun and Nachtwölfe) who work feverishly toward world domination, the Naga prefer working in the shadows. They never show their hand or reveal their influence unless they have no choice.
- Tcho-Tcho: Cannibalistic psychopaths with a tragic past. They were a group of men and women in Southeast Asia from the far future who had managed to keep their sanity in the face of the horrors occurring all around them. Death, chaos, devastation, madness, and despair brought about by the return of the Eldritch entities of the Mythos. They figured out a way to open a portal to the past, where they could escape to a time before the end times and warn the world (and prevent it from happening). Unfortunately the calculations were off and they went too far back in time. Not only that but their minds were deteriorating as their brains were slowly dying off. They managed to find a way to hold it off, by creating a vaccine from human blood. Tragically over time they became mad, forgot their reason for coming back in time, and turned to cannibalism.
- Section M: A British multinational organization which recruits from members of the British Empire and the member states of the Commonwealth. It also recruits from among the refugees that have fled war torn Europe. It is made up of amateurs, who are gifted and determined.
- Majestic (MJ): Which is an American organization established under order of FDR within the OSS to fight the Mythos-related threats. Unlike the relationship between the American and British intelligence services which is "fraught" at best, Majestic and Section M have a good relationship. Cooperating and sharing information, they have developed a sense of kinship with each other.
- Brain Institute: It's a secret organization within the Soviet Union which keeps Lenin's brain "alive" via recovered Mi-go technology. The Brain Institute of the VKP (b) which answers only to the Communist Party. Lenin takes an active part in political life, and advises Stalin. Within the Brain Institute, is a secret organization, the Cult of the Red Horus. Which worships Lenin as a god. The cult is a sorcerer heavy society.
- Institute 21: Which is a shadowy division of the NKVD (secret police). It employs Russian occultists and sorcerers for the betterment of the state. A considerable number of its staff work for the Institute because the other option is being executed or a slow death in the Gulag. It's the sorcerous right hand of SMERSH, supporting counter-intelligence with dark rituals and profane artifacts. They work for the NKDV, not the state and its staff are loyal only to Colonel Sevastyan Solokov, the founder of Institute 21.
- Otdel MI (Otdel Mejmirovyh Issledovanyi): Bureau of Extraplanar Research. It is part of the NKVD and has the support of many high-ranking Soviets in its struggle against occult SS groups and rogue sorcerers. They send their researchers across the world to collect ancient books, relics, and artifacts. Some have visited other worlds and dimensions. They suspect that Institute 21 is controlled by dark powers and view its destruction as necessary for the survival of not only the Soviet Union, but the entire world. It co-operates with Section M and Majestic in their battle with German occult groups, though it has also spies on those organizations.