It was a war to protect the sovereignty of Japan and secure Japanese rights and interests in the peninsula by preventing the southward expansion of the Russian Empire (the domination of Korea), which established a presence in Northeastern part of China (Manchuria) after the Triple Intervention and the Boxer Rebellion.
三国干渉および北清事変後中国東北部(満州)を勢力圏としていたロシア帝国による朝鮮半島への南下（朝鮮支配）を防ぎ、日本の安全保障と半島での利権を確保することを目的とした戦争。