After the fall of the Roman Empire, Charlemagne became king of the Frankish people in the year 751. He had the main belief of unifying all Germanic peoples and convert them to Christianity. Other important beliefs he had were the revival of culture and education which had been relegated during the dark ages. Thanks to these beliefs, Charlemagne got to control a large part of Europe. They are important for a ruler since promoting education within it citizens helps the development of a society. The firm belief he had in uniting all peoples is represented in many rulers that followed him like Napoleon; it is an important principle to consolidate a government and peace in a territory. Another example that he set for future leaders is the ability to make strategic alliances, the one he made with the Catholic Church eventually turn him into the holy roman emperor.
The British did all of the following things mentioned in the question above.
I know that manifest destiny was the mindset of Americans that they were destined to stretch from coast to coast.
The Louisiana purchase was during that time. Napoleon didn't have the troops to keep Louisiana so he sold it to us for cheap.
The transatlantic slave trade began during the 15th century when Portugal, and subsequently other European kingdoms, were finally able to expand overseas and reach Africa. The Portuguese first began to kidnap people from the west coast of Africa and to take those they enslaved back to Europe.
