With the peace treaty between the Oda and Tokugawa done in 1562, an alliance that lasted twenty years, a rarity in the Sengoku Era. This was very important. Without the alliance, Nobunaga would have never conquered Mino or made his presence known in Kyoto in 1568. Ieyasu would have never had the chance to clean up Mikawa either. He still would have been in the service of the Imagawa.
Here are some facts about the alliance. Nobunaga was the senior partner, no doubt about it.
Jeroen Lamers, Japonius Tyrannus, page 49 has most of the answers.
- Ieyasu was not a direct vassal of Nobunaga.
- He was on independently on par with Nobunaga's captains, but did not have to listen to them.
- However, he did take orders directly from Nobunaga.
Nobunaga and Ieyasu did team up together in 1570 to score a victory over the Azai/Asakura at the Battle of Anegawa in 1570.
Tenka no tame!