Hearts of Iron IV is a grand strategy game by Paradox Interactive released in 2016, set during World War II. Its event system delivers focus completions, political changes, and historical moments through pop up windows, each introduced by this notification sound. As HOI4 clips spread on YouTube and TikTok, the pop became shorthand for receiving major news in any context. It sits alongside other game UI sounds creators reuse, such as the GTA V notification and the Fears to Fathom Notification Sound, but HOI4 fans recognise its pop instantly.