Toyotomi Hideyoshi (then not of this name) was Oda Nobunaga's vassal. Tokugawa Ieyasu was Oda Nobunaga's ally.

After Nobunaga was betrayed and killed by his vassal Akechi Mitsuhide, Hideyoshi was able to defeat Mitsuhide, then convince Nobunaga's other vassals to work for him. Those who wouldn't do so sided with Nobunaga's sons against Hideyoshi but were defeated. During this Ieyasu was either neutral or hostile. After the last of Nobunaga's vassals who resisted Hideyoshi was defeated, after much negotiations Ieyasu also agreed to become Hideyoshi's vassal. This continued until Hideyoshi's death, on which Ieyasu made his own move for power.