samurai-dominated government and relegating the emperor to figurehead status. However, the Taira clan was still very conservative when compared to its eventual successor, the Minamoto, and instead of expanding or strengthening its military might, the clan had its women marry emperors and exercise control through the emperor. The Taira and the Minamoto clashed again in 1180, beginning the Genpei War, which ended in 1185. Samurai fought at the naval battle of Dan-no-ura, at the Shimonoseki Strait which separates Honshu and Kyūshū in 1185. The victorious Minamoto no Yoritomo established the superiority of the samurai over the aristocracy. In 1190 he visited Kyoto and in 1192 became Sei'i Taishōgun, establishing the Kamakura shogunate, or Kamakura bakufu. Instead of ruling from Kyoto, he set up the shogunate in Kamakura, near his base of power. "Bakufu" means "tent government", taken from the encampments the soldiers would live in, in accordance with the Bakufu's status as a military government. After the Genpei war, Yoritomo obtained the right to appoint shugo and jitō, and was allowed to organize soldiers and police, and to collect a certain amount of tax. Initially, their responsibility was restricted to arresting rebels and collecting needed army provisions and they were forbidden from interfering with Kokushi officials, but their responsibility gradually expanded. Thus, the samurai class became the political ruling power in Japan. Ashikaga shogunate and the Mongol invasions Various samurai clans struggled for power during the Kamakura and Ashikaga shogunates. Zen Buddhism spread among the samurai in the 13th century and helped to shape their standards of conduct, particularly overcoming the fear of death and killing, but among the general populace Pure Land Buddhism was favored. In 1274, the Mongol-founded Yuan dynasty in China sent a force of some 40,000 men and 900 ships to invade Japan in northern Kyūshū. Japan mustered a mere 10,000 samurai to meet this threat. The invading army was harassed by major thunderstorms throughout the invasion, which aided the defenders by inflicting heavy casualties. The Yuan army was eventually recalled, and the invasion was called off. The Mongol invaders used small bombs, which was likely the first appearance of bombs and gunpowder in Japan. The Japanese defenders recognized the possibility of a renewed invasion and began construction of a great stone barrier around Hakata Bay in 1276. Completed in 1277, this wall stretched for 20 kilometers around the border of the bay. It would later