The Sino-Japanese Empire, commonly referred to as Sino-Japan, is a country in Eastern Asia. It was established in 1856, with the marriage of the Imperial Japanese and Chinese families, and the uniting of their two realms into one empire. Established to protect itself from Russian encroachment, the empire rapidly industrialised and advanced both militarily and economically. The empire began the Asia-Pacific War to gain more land and resources for its massive population, currently estimated at 1.8 billion.