After Russia occupied the Danubian Principalities in 1769–70, Frederick's representative in Saint Petersburg, his brother Prince Henry, convinced Frederick and Maria Theresa that the balance of power would be maintained by a tripartite division of the Polish–Lithuanian Commonwealth instead of Russia taking land from the Ottomans. They agreed to the First Partition of Poland in 1772, which took place without war. Frederick claimed most of the Polish province of Royal Prussia. Prussia annexed and 600,000 inhabitants, the least of the partitioning powers. However, Prussia's Polish territory was also the best-developed economically. The newly created province of West Prussia connected East Prussia and Farther Pomerania and granted Prussia control of the mouth of the Vistula River. Frederick also invited German immigrants to the province, hoping they would displace the Poles. Maria Theresa had only reluctantly agreed to the partition, to which Frederick sarcastically commented, "she cries, but she takes".