Final answer:
The feudal system in Japan contributed to the presence of private armies due to decentralized power, as regional warlords controlled their own territories and raised private armies to defend and expand their influence.
Step-by-step explanation:
The feudal system contributed to the existence of many private armies in Japan due to decentralized power. In this system, regional warlords known as daimyo were granted control over their own territories and were responsible for maintaining law and order. As a result, they raised their own private armies to defend their lands and expand their influence. This decentralization of power allowed for the proliferation of private armies throughout Japan.