By the 18th century, the Russian Empire extended its control to the Pacific, peacefully forming a common border with the Qing Empire and Empire of Japan. This took place in a large number of military invasions of the lands east, west, and south of it. The Polish–Russian War of 1792 took place after Polish nobility from the Polish–Lithuanian Commonwealth wrote the Constitution of 3 May 1791. The war resulted in eastern Poland being conquered by Imperial Russia as a colony until 1918. The southern campaigns involved a series of Russo-Persian Wars, which began with the Persian Expedition of 1796, resulting in the acquisition of Georgia (country) as a protectorate. Between 1800 and 1864, Imperial armies invaded south in the Russian conquest of the Caucasus, the Murid War, and the Russo-Circassian War. This last conflict led to the ethnic cleansing of Circassians from their lands. The Russian conquest of Siberia over the Khanate of Sibir took place in the 16th and 17th centuries, and resulted in the slaughter of various indigenous tribes by Russians, including the Daur, the Koryaks, the Itelmens, Mansi people and the Chukchi. The Russian colonization of Central and Eastern Europe and Siberia and treatment of the resident indigenous peoples has been compared to European colonization of the Americas, with similar negative impacts on the indigenous Siberians as upon the indigenous peoples of the Americas. The extermination of indigenous Siberian tribes was so complete that a relatively small population of only 180,000 are said to exist today. The Russian Empire exploited and suppressed Cossacks hosts during this period, before turning them into the special military estate Sosloviye in the late 18th century. Cossacks were then used in Imperial Russian campaigns against other tribes.