Charlemagne was able to .

As you didn't specify what exactly is required, I am guessing the correct answer that is requested here is - Charlemagne was able to bring together and unit a big portion of Western Europe during the early middle ages under one banner. This is his most known achievement, or at least the one that is most talked about. Furthermore, doing this he helped lay out the foundations for countries that would be later known as France and Germany :)