Why did Tokugawa Ieyasu submit to Toyotomi Hideyoshi after opposing him?

After the death of Oda Nobunaga in 1582, Tokugawa Ieyasu emerged as the primary rival to Toyotomi Hideyoshi, who had moved to seize control of Japan. Following a series of bloody but indecisive military skirmishes between the two, Ieyasu—known for his cautious nature—chose to offer a vow of fealty to Hideyoshi.1

This strategic submission proved mutually beneficial: Hideyoshi was content to leave Ieyasu’s existing domain intact, allowing Ieyasu to avoid further conflict while he focused on strengthening his administration, increasing the productivity of his lands, and enlarging his vassal force. By submitting, Ieyasu secured the stability necessary to consolidate his power, eventually positioning himself to become the preeminent leader of Japan following Hideyoshi's death in 1598.12