George Eldon Ladd in The Presence of the Future:
God is the Lord of history; but there are hostile elements, opposing forces that seek to frustrate God's rule. It is not the biblical view that ... all of history moves toward the Kingdom of God. There are demonic forces manifest in history and in human experience which move against the Kingdom of God. Evil is not merely absence of good, nor is it a stage in man's upward development; it is a terrible enemy of human well-being and will never be outgrown or abandoned until God has mightily intervened to purge evil from the earth.
Christians can enjoy fulfillment of Old Testament prophecy and blessings in this present age while at the same time look forward to a final and glorious fulfillment. Because of the First Coming of Jesus Christ, we now possess the complete fulfillment and blessings of the promises concerning the messianic age. At the same time this age brings a new series of promises to be fulfilled at the end of the age. The fulfilled promises give us greater hope and anticipation of the glory yet to come.
With his first advent, the Kingdom of God and the "last days" arrived indicating that Old Testament expectation had turned to New Testament fulfillment.
Kim Riddlebarger describes three basic elements of New Testament eschatology in A Case for Amillennialism.
The first of these is that the Old Testament promise of a coming Redeemer was realized in Jesus Christ. ... With his first advent, the kingdom of God and the "last days" arrived, indicating that Old Testament expectations had turned to New Testament fulfillment.
The second basic element of New Testament eschatology is that what was understood as one glorious messianic age predicted in the Old Testament unfolded in two different ages: "this age" and "the age to come." ... The coming of Jesus Christ marked the beginning of a glorious new redemptive age with a corresponding set of blessings. Yet this new age is not fully consummated and will be fulfilled in the future. This already/not yet structure gives the New Testament a strong forward-looking focus. The New Testament contains a distinct and pronounced tension between what God has already done in fulfilling the promises of the Old Testament and what God will do yet in the future.
The third element of New Testament eschatology is that the present blessings of the coming Redeemer are the pledge of greater blessings to come. Christ's first advent guarantee his second coming.