It's important to rely on verified historical information, and this particular detail about Tojo's equestrian habits hasn't been documented.
What breed of horse did Tojo ride?
There's no record of Tojo, the Japanese Prime Minister during World War II, riding any specific breed of horse. He is not known to have been an avid equestrian. While some high-ranking Japanese officials were known for their equestrian pursuits, there's no evidence that Tojo was among them.