Satan's demons rule over territories. The ranks get lower as the territories gets smaller. There was a demon prince over Persia that held up the messenger angel sent by God to Daniel for 21 days. An earthly prince could not of lasted 21 seconds against an angel. Remember the angel of the LORD went forth, and smote in the camp of the Assyrians a hundred and fourscore and five thousand: and when they arose early in the morning, behold, they were all dead corpses. There was the demon prince assigned over Persia (now called Iran), and Greece had one too. Maybe each continent has a demon king over it, each country a demon kings and princes (Iran, and Greece do). Then all states have a demon archduke, and counties have a duke all the way to down to you and me having demons assigned to us. The legion of demons did not want to leave their country because demons are territorial.
Daniel 10:12 Then said he unto me, Fear not, Daniel: for from the first day that thou didst set thine heart to understand, and to chasten thyself before thy God, thy words were heard, and I am come for thy words.
13 But the prince of the kingdom of Persia withstood me one and twenty days: but, lo, Michael, one of the chief princes, came to help me; and I remained there with the kings of Persia.
14 Now I am come to make thee understand what shall befall thy people in the latter days: for yet the vision is for many days.
15 And when he had spoken such words unto me, I set my face toward the ground, and I became dumb.
16 And, behold, one like the similitude of the sons of men touched my lips: then I opened my mouth, and spake, and said unto him that stood before me, O my lord, by the vision my sorrows are turned upon me, and I have retained no strength.
17 For how can the servant of this my lord talk with this my lord? for as for me, straightway there remained no strength in me, neither is there breath left in me.
18 Then there came again and touched me one like the appearance of a man, and he strengthened me,
19 And said, O man greatly beloved, fear not: peace be unto thee, be strong, yea, be strong. And when he had spoken unto me, I was strengthened, and said, Let my lord speak; for thou hast strengthened me.
20 Then said he, Knowest thou wherefore I come unto thee? and now will I return to fight with the prince of Persia: and when I am gone forth, lo, the prince of Grecia shall come.
In Daniel 10:13 the Greek translation for kings is meh'-lek which means king single or royalty and not kings plural.
Demons are territorial
Mark 5.9. And he asked him, What is thy name? And he answered, saying, My name is Legion: for we are many.
10. And he besought him much that he would not send them away out of the country (geographical region).