From The Dog Shogun: The Personality and Policies of Tokugawa Tsunayoshi, by Beatrice Bodart-Bailey (U. Hawai‘i Press, 2006), pp. 10-11:
Tokugawa Ieyasu (1542-1616) has gone down in history as one of Japan’s great unifiers, the third and last of three generals who ended over a century and a half of sporadic local warfare and ushered in some two and a half centuries of unbroken peace. Yet while in hindsight we recognize in Ieyasu the first of an unbroken line of fifteen Tokugawa shoguns, the future of Tokugawa rule looked much less certain to his contemporaries.
“His Majesty … has reasons to fear for his life, for there is the example of his predecessors. This kind of empire is only acquired by force of arms and is retained by the use of tyranny,” mused the Spaniard Rodrigo de Vivero y Velasco (1564-1636) when he visited Ieyasu at his retirement seat at Sunpu. The future viceroy of Mexico, who had been shipwrecked in Japan en route to his appointment, marveled at the strength of the fortifications of Ieyasu’s castle, only outdone by those of Edo, where Ieyasu’s son, Hidetada, was conducting the government. In Edo some twenty thousand men were, in de Vivero’s estimation, assigned to duty between the outer defenses ringed by the moat and the inner palace of the ruler, but he noted that Ieyasu at Suruga had a larger contingent of troops stationed nearby.
Life had presented Ieyasu with plenty of opportunity to observe the dangers befalling a ruler. Born as the son of a minor feudal lord in a period known as the “Warring States,” he had spent his youth as hostage to a neighboring clan. Though the emperor was still residing in unbroken lineage at his capital of Kyoto, political authority was split between a large number of military houses, attempting to enlarge their sphere of influence or simply to survive. The bond between lord and retainer was feudal in character, but considerations of loyalty were all too often eclipsed by strategic interests. This lack of loyalty was so prominent that the Jesuit Alessandro Valignano (1539-1606) considered it one of the two greatest defects of the Japanese. He ranked it second only to their sexual promiscuity. Hence the period is characterized by the phrase gekokujou, “inferiors overthrowing superiors.”