In 1603, a Tokugawa shogunate (military dictatorship) ushered in a long period of isolation from foreign influence in order to secure its power. For 250 years this policy enabled Japan to enjoy stability and a flowering of its indigenous culture. Following the Treaty of Kanagawa with the United States in 1854, Japan opened its ports and began to intensively modernize and industrialize. During the late 19th and early 20th centuries, Japan became a regional power that was able to defeat the forces of both China and Russia. It occupied Korea, Formosa (Taiwan), and southern Sakhalin Island. In 1933 Japan occupied Manchuria and in 1937 it launched a full-scale invasion of China. Japan attacked US forces in 1941 - triggering America's entry into World War II - and soon occupied much of East and Southeast Asia. After its defeat in World War II, Japan recovered to become an economic power and a staunch ally of the US. While the emperor retains his throne as a symbol of national unity, actual power rests in networks of powerful politicians, bureaucrats, and business executives. The economy experienced a major slowdown starting in the 1990s following three decades of unprecedented growth, but Japan still remains a major economic power, both in Asia and globally. In 2005, Japan began a two-year term as a non-permanent member of the UN Security Council.