Why were mother countries able to expand into foreign lands

Mother countries, expression coined in the USA from the early European settlers to refer their native land or the land of their ancestors from which the people of a colony was derived,  had a global expansion between the 1760s and the 1870s because of several reasons. Among the reasons that allowed mother countries being able to expand into foreign lands highlights their superior technology and medical knowledge.

Their medical knowledge helped Europeans to survive tropical diseases and allowed them to penetrate the insides of Africa and Asia, which were mosquito-infested. On the other hand, their superior technology in terms of their steamboats and the telegraph enabled these countries to increase their mobility and to quickly respond to situations that could threaten their dominance.

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jim crow laws were enacted in northern states.