The american civil war beacause you cant just search only that up. You will get lots of answers beacuse more than one thing happened then.
Answer: One reason the U.S. got involved in the Vietnam War was that it was a conflict between communism and a freer system. The communist system cannot produce as much wealth as it consumes because its producers are forced to react to political motives instead of economic motives.
Explanation:
They gained increases economics
The passage of the Kansas- Nebraska Act
In this context alliance would mean to come to a formal agreement to help each other.