They were all barriers for the colonial period
An Automobile should be a possible answer i do hope this helps
The commanding general and his troops were overly confident of victory and took foolhardy chances in battle.
It was basically a the transportation of African slaves to America. This occurrance took place between the 16th and the 19th century.
In this trade slaves were sold to Western Europeans which then resold the slaves to the Americans. The first ones to engage in this "programme" where the Portuguese, who took slaves to Brazil for the first time about 26 years they arrived there in 1500.
Hope it helped,
BioTeacher101
