When the Monroe Doctrine was written, the US had just formed and was not ready to fight the European powers. Monroe basically asked Europe to stay out of the Western Hemisphere because they were afraid of getting attacked.
The creator, James Monroe, was interested in keeping the United States out of a war it was not prepared for. Though it was out of fear, there was some thinking through; people voted on it, after all.
Note that by "afraid of getting attacked," I not only mean getting attacked through soldiers and cannons but also by taking over nearby areas and competing with the US for natural resources.
It means - a forcible overthrow of a government or social order, in favor of a new system.
The man being described here is Prince Henry the Navigator. Prince Henry was a Portuguese man who helped spark the age of exploration. He is known for his several contributions to this era, including:
1) Opening of a school for navigation in Sagres, Portugal.
2) Mapping the west coast of Africa.
3) Laid the foundation for individuals like Christopher Columbus, Vasco Da Gama, and John Cabot.
The Chinese Exclusion Act of 1882 was the first significant law restricting immigration into the United States. Those on the West Coast were especially prone to attribute declining wages and economic ills on the despised Chinese workers.
