Same thing from the other question I answered.
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.
Yes it is its not allowed to trade with other countries
<span>He was killed before a trial could begin. </span>
