From a layman's understanding,
One's millennial view is only one part of one's eschatological view.
Historic premillennialism (not the modern dispensational kind) existed as a view in the very early church but amillennialism has been, by far, the majority report in Christianity historically. There are various views within amillennialism that have been the primary debate historically such as whether there is a national conversion of the Jews, whether things get much better or much worse right before our Lord's return, etc. But those are all in-house views within amillennialism.
Some may not agree here, but the more I study postmillennialism, the more it seems to have in common with amillennialism. It's almost as if it is a form of postmillennialism. That's why some can see something of postmillennialism in theology as far back as Augustine.
Remember that "a"millennialism means a 'realized' millennium, which began when Jesus ascended and exists now. Jesus is reigning in heaven and will return at the second coming as Judge and for the resurrection of both the living and the dead. At that time, He will fully and finally put the last enemy death under His feet. In the meantime, His Kingdom exists and is being manifest in the lives of His people, a spiritual kingdom.
The modern dispensational premillennialist position began with Mr John Nelson Darby and the Plymouth Brethren, middle 1800's. It sees our Lord's reign as wholly future (and limited to man's [Julian] calendar). It also sees two "Kingdoms"- an "earthly" one that is future for Israel and a "spiritual" one, also future for "the church." It has gone through many changes and is now very confused about what happens to people who have some Jewish blood and which set of promises they have and whether the two "kingdoms" eventually get together. [reformed theology says it is all now, since Christ ascended].
