The power struggle between popes and kings?

Answer 1

In the past, such as the Middle Ages, the pope had immense power. This was because nearly everyone went to church back then (namely the Catholic church, which the pope belongs to), thereby giving the pope extreme power. (Hence the common corruption/misuse of power when it came to the popes-- though that is a matter of opinion.) Due to being at the head of such power, the pope acted as someone of, well, power. However, they weren't supposed to be the head of the power. The king(s) was. And so a power struggle is what ensued, with the Church (pope) wanting or possessing power that, by law, belonged to the king. And, of course, the pope held power over the church people, complicating the problem. This power struggle shows what it means to have a separation between church and state, and to have a lack of one. An example of this power struggle is with Pope Leo III and Charlemagne. Read about it at the link below. Remember to read Part II to get the whole picture.

Answer 2

That millenia-old conflict has always been about power over individuals. Religious and secular leaders' conflicts were partially resolved at the Council of Nicea, which basically was a truce, providing that religious leaders would have power over individuals in the next life, and secular leaders in this. It has always been an uneasy truce, and in our times, it has been breaking down and religion asserts a more muscular role in global politics, and coming into conflict everywhere with conflicting belief systems; hence the armed religious conflicts breaking out all over the world.