Why didn't the Roman Empire conquer Ethiopia?

The Roman Empire, contrary to popular belief, did not go around looking for territories to conquer. Every country that became part of it had been involved in wars that had drawn the Romans in. They never had a reason to invade Ethiopia. read more

Neither Russia nor any of its predecessors existed at the time Roman Empire collapsed. There was also so-called Eastern Roman Empire (Byzantine Empire) which was really an empire of Greeks, not Romans. It managed to last until XV century, so for some time it existed in parallel with Grand Duchy of Moscow - the predecessor of Russian Empire. read more

up vote 11 down vote favorite I know that the Romans when they were on their empire's peak around the 1st and 2nd century AD, controlled the northern coast of Africa and had the Sahara desert as some kind of natural "wall" as well as border of which they thought that it is the end of the world so they did not bother to explore it. read more