The origins of the medieval world

The origins of the medieval world can be traced back to Roman times with both the rise of the Catholic Church and the influence of various Germanic tribes.
Both emerged by the 8th and 9th centuries as dominating institutions, controlling both the temporal and spiritual realms of Western Europe, but their power
was developed and crafted over centuries.
Which were the most important developments for both the Church and the Germanic tribes when tracing their rise through the early medieval period?