Diocletian and Constantine were famous as the people who completely reformed the military system and created a new system of government, which gave new life to the late roman empire.
A country or area in which another country has power to affect developments although it has no formal authority.
The plague stopped the movement plus lack of technology
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The Portuguese were among the first Europeans to explore the
seas beyond Europe. Henry the Navigator urged his father, King John I, to
conquer the port of Ceuta in Northern Africa. He also sponsored the development
of the Caravel, a sailing ship that is lighter and faster than most ships at
that time. Use of caravels enabled sailors to travel further and with more
provisions, and the light draft enabled Portuguese sailors to explore shallow
rivers and waters. He also sponsored explorations to Madeira, Azores, and West
Coast of Africa.