You just keep checking more boxes into what fits the description of a vassal state. Being a vassal state has benefits. Protection being one of them. The Japane

You just keep checking more boxes into what fits the description of a vassal state. Being a vassal state has benefits. Protection being one of them. The Japanese people are smart, they saw their options and realized being a vassal state of the US (and not the Soviet Union) was in their best interest.