the prince of the kingdom: Spiritual forces behind different nations, like the spirit prince of Persia or Greece, blocked the way of God's messenger who responded to the prayers of God's people (see Daniel 10:20–11:1).
one of the chief princes: An archangel is a chief among God's heavenly messengers.
Daniel's world, and ours, has more than what we can see. Daniel learns that history's great events happen against a real spiritual backdrop. In this world, spiritual beings either support or hinder God's people, and age-old conflicts play out. Behind everything, the Ancient of Days guides all things and judges the process and its outcome.
God's covenant with his people and their relationship with him through prayer are central. The world is not ultimately governed by angels and spirit princes, but by the Ancient of Days, who hears his people's prayers.