Tillich: Your God is your ultimate concern.
Religion is more than it seems. People may be faithful practioners of a religion without having any awareness of it. For example the super-patriots of any country often put their flag ahead of their supposed God. Something has to come first; to really believe 'my country, right or wrong' means that 'your country' is ahead of what you think of as God. You may ostensibly be a faithful and zealous Christian, but if the Christian God comes second to your country, that simply means you worship another God. (Many theologians use the term idol, which relates this thought to the idolatry so deplored in the O.T.; however O.T. writers used god in the same way.
In the realm of religion we give people various names that have various meanings; for example the name, Christian, means quite a lot of things besides putting Christ at the top of your priority. You may primarily worship your family and still consider yourself a good Christian. Whatever you worship is your religion.
This is brought home with great urgency by a man named Walter Wink, who has written a series of books in this vein. He introduced many of us to the 'domination system', which he suggests has largely taken the place of the 'Christian system'.
Those in the shadow of the 'domination system' worship power: power for themselves, power for those stronger people they have attached themselves to, power over the 'others'. The exercise of power over others is the basic form of violence. He who exercises power may find it necessary to kill someone 'for their own good'.
The book of Genesis refers to a man named Nimrod: "a mighty one in the earth (The Jerusalem Bible translates this "the first potentate").
10:9 He was a mighty hunter before the LORD ("The term is not complimentary, but implies ruthlessness and a lust for power." cf
Lambert Dolphin's Library)
10:10 And the beginning of his kingdom was Babel (where God confounded the tongue of those attempting to build a tower into heaven)
(In Micah 5:6 Nimrod is associated with Assyria-- the bloodiest, most brutal and savage nation that Israel ever encountered.)
Throughout the book of John you will see this eternal conflict acted out in the tension between Jesus and the civil, religious and military authorities where he lived.