I still remember that I was really annoyed when I learned about Tsunenaga in my middle school’s Japanese history class because I had to connect my knowledge of both Japanese history class and world history class. They were about the same thing in the end, but combining the different points of view together to understand the whole was quite confusing for a lazy middle school girl.
Anyway, the so-called “Age of Discovery” started in the 15th century. There were many reasons for this such as the need for new trading routes due to the blooming of the Ottoman Empire, the development of a compass suitable for long voyages, more reliable ships, establishment of strong dynasties like Portugal and Spain etc. This is what we learned in world history class.
In Japanese history class, the term “Age of Discovery” doesn’t really apply. We didn’t discover anything and our islands continued on as they had been forever, so there were no discoveries at all for us. So we call it the “Age of the Great Navigation” instead.
This is an interesting coincidence of history. The “Age of the Great Navigation” fit perfectly in the midst of the Sengoku Era. Japan was in chaos. The central government lost its power and dignity and local lords then started to rule their own territories independently and fought with each other for supremacy of Japan.
Basically, if you had the talent, you would be the future king! It was that kind of situation and Masamune was one of the candidates!