The Russian Empire, also known as Imperial Russia or simply Russia, was a vast realm that spanned most of northern Eurasia from its proclamation in November 1721 until its dissolution in March 1917. At its height in the late 19th century, it covered about 22,800,000 square kilometres (8,800,000 sq mi), roughly one-sixth of the world's landmass, making it the third-largest empire in history, surpassed only by the British and Mongol empires; it also held colonies in North America between 1799 and 1867. The empire's 1897 census, the only one it conducted, found a population of 125.6 million with considerable ethnic, linguistic, religious, and socioeconomic diversity.

The Polish–Lithuanian Commonwealth, formally known as the Kingdom of Poland and the Grand Duchy of Lithuania, or simply Poland–Lithuania, was a bi-confederal state, sometimes called a federation, of Poland and Lithuania ruled by a common monarch in real union, who was both King of Poland and Grand Duke of Lithuania. It was one of the largest and most populous countries of 16th- to 17th-century Europe. At its largest territorial extent, in the early 17th century, the Commonwealth covered almost 1,000,000 km2 (400,000 sq mi) and as of 1618 sustained a multi-ethnic population of almost 12 million. Polish and Latin were the two co-official languages, and Roman Catholicism served as the state religion.