Answer:
a) blockade the southern ports from supply ships
Explanation:
By forming various organizations.
The European Union, for example, unites Europe (Minus Britain these days) under one banner, thus preventing fighting.
A more direct example is the North Atlantic Treaty Organization. NATO protects the "North Atlantic" and Europe from terrorists and invading countries by using the combined military strength of multiple nations.
Answer:
The great lakes are in between the USA and Canada
