Before sixteenth century, Japan was in a state of war lord time. As long as you could gather man power to follow you, you would be a leader of that territory. Then, you became a warlord to administer the territory under your control.
If your territory was not big, you could only be a small warlord and you have to be a satellite to a big warlord who will then protect you in case that you were attacked by other warlord.
War frequently fought between big warlords and small warlords had to fight for big warlords to whom he was in allies.
Tokugawa was small warlord in the beginning, but slowly he extended his territory to a very large area of Japan. Many warlords in different parts of Japan obeyed him as a leader.
At the year of 1600, Tokugawa, at his age of fifty eight, fought a famous war called “Battle of Sekigahara”. He won the war and his name became very famous and he held full power to administer whole Japan. From that time on he united Japan to one country and for the next two hundred sixty five years, historian named that period as “Tokugawa Time”.
One Japan writer described Tokugawa as a man of greedy, short in size, fat in body, fond of sex greatly. But, he had a very good point. That is his tolerance and patience. He never showed his ambitions while he was under a big warlord when he thought he was not strong enough to win. His motto was “patience and patience” until the time was ripe in favor of him.