LORE.

Europe is in shambles, after the Russo-Turkish War of 1787... a new Virus appeared. It started as a virus that killed, though reanimated people, turning them into cannibals during Napoleon's Invasion of Russia.. where after the Moscow burning.. everything turned into hell.

The men trapped at Berezina after the retreat of Napoleon sacraficied their lives so others could escape the fate of the hordes that showed no empathy for the injured, alive, and sick... instead it only killed and ate men, turning them into wicked savages. The men who survived that nightmare told stories as the hordes came, tearing through Prussia, Russia, Austria, The German States, Bavaria, Baden-Württemberg, Hanover, Saxony & many other German states, with France being killed mercilessly, as the hordes entered into the gates of Paris, Burnt Copenhagen... and entered Spain.. with Königsberg being a remaining part of Prussia and lasted for 2 years till it fell.. and now.. there was America standing by seeing Europe in shambles.

Britain had made peace with America on 1815 and had began receiving aid... it would just determine in the future though of what would America do.