Angels in History and Prophecy

A Dispensational Study of the Ministry of Angels. What are the different orders of angels? When were the angels created? What are angels like? Who are the "sons fo God" of Genesis 6? Do Christians have guardian angels? Will angels fight at Armageddon? Angels were active in ministry in Old Testament times and during the ministry of Jesus. Angels were also active during the time of the very early Jesish church age, but there are very few references to angels after Acts 13 and the epistles to the churches. But suddenly in Revelation there are scotes of references to angels. Why? What will be the rold of angels in the Millennium?