From the early time to the middle ages the political and economic power of Japan was in the hands of noble dynasties. In the late 13th the various Japanese royal families were united against the common enemy - Mongol invaders. The turning point in the history of the country was from 1600 till 1868 when the actual unification of Japan began. In the 19th century a Western-style system of administration was established, which stimulated a rapid industrialization. The Japanese took little active part in World War I, despite the fact that Japanese factories produced munitions and supplies for the Allies. During World War II the country acted on the side of Germany. Japan was occupied by American troops, and in 1946, the Americans imposed the constitution that governs Japan today. After suffering massive destruction during WWII, Japan was the economic phenomenon of the late 20th century. In 1990 Japan adopted a more substantial foreign policy, and some modifications to the constitution were declared.