Seven Years' War
Though the Seven Years' War involved all of the major powers in Europe, they were aligned primarily between France and Great Britain and for the most part was fought in the Holy Roman Empire (Germany).
Its effect on the German population so closely following the previous 200 years of fighting was devastating with widespread poverty, religious intolerance, heavy taxation, malnutrition, and continual threat of military conscription.
All of these conditions were contributing factors in the decisions of many to accept the terms of Catherine's Manifesto which extended an invitation of immigration to Russia.
For an in depth description on the geo-political reasons and repercussions of the Seven Years' War please see any of the following:
- Encyclopædia Britannica - Seven Years' War (European History)
- Wikipedia - Seven Years' War
- This History of War - Seven Years War (1756-1763)