Final answer:
Tokugawa Ieyasu protected Japan from foreign ideas he considered dangerous by isolating the country, expelling Christian missionaries, and limiting Japanese travel abroad. This period of Japanese history is characterized by enforced isolation to preserve traditional values and prevent foreign influence.
Step-by-step explanation:
What did the samurai Tokugawa Ieyasu do to protect Japan from the effects of what he considered dangerous foreign ideas? Tokugawa Ieyasu chose to isolate Japan from dangerous foreign ideas. Concerned by the spread of Christianity and the possibility that it could undermine his rule and the stability of the country, he enacted policies that would dramatically reduce foreign influence.
In 1614, Ieyasu outlawed the practice of Christianity and ordered missionaries to leave the country. He warned Japanese Christians to renounce their faith or face persecution. Furthermore, to maintain control and prevent conspiracies, he banned Japanese from travelling abroad and limited foreign access to Japan. The only exceptions for foreign trade were at the port of Nagasaki, and this was strictly with the Chinese and the Dutch. By restricting these interactions, Ieyasu aimed to preserve the traditional Japanese way of life and Neo-Confucian ideas that he deemed essential for the nation's governance and culture.
The exclusionist policies of the Tokugawa shogunate were somewhat successful in preventing the spread of foreign ideas. However, it also resulted in Japan falling behind in scientific and technological advancements during this period of self-imposed isolation, known as sakoku.