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.
One of the main reasons for the civil war was the differences with slaves about whether it was illegal or legal to have slaves. This could have been avoided if there was agreement on how slaves should be treated.
Roanoke Jamestown and is England
<span>fffffffffffffffifty years ago, the U.S. enacted a sweeping immigration law, the Immigration and Nationality Act, which replaced longstanding national origin quotas that favored Northern Europe with a new system allocating more visas to people from other countries around the world and giving increased priority to close relatives of U.S. residentsssssssssssssss.</span>
Here this will help you http://indicatorloops.com/portmoresby.htm
