This scenario is the least likely, but still could happen someday in some similar fashion some time in the more distant future. The Islamic Caliphate manages to take over all of the territories it claims in the “5 Year Expansion Plan” posted by ABC News, which pretty much includes the Balkans, Central Europe, Spain, Crimea, the Middle East, Turkey, North Africa, India, Sri Lanka, Central Asia, the Caucuses, Iran, Afghanistan, Pakistan, Bangladesh and parts of China, Ukraine and Moldova.
To stop it’s expansion, the EU, Russia, China and NAU band together to wage war against it. It’s a highly unlikely scenario for the next 50 years or so, but it’s fun to conduct an experiment using current numbers to visualize if this happened in the 2019-2020 period.