What strategy did both Toyotomi Hideyoshi and, later, Tokugawa Ieyasu use to create peace in Japan?

The strategy they used was "sword hunting."

Explanation:

In 1588, Hideyoshi forbade ordinary peasants to possess arms and began "sword hunting" to confiscate weapons. The swords were melted to create a Buddha statue. This measure effectively stopped the peasant revolts and ensured greater stability to the detriment of the freedom of individual daimyos. This prevented the constant internal conflicts and civil war in the country, creating a time of peace and stability.