Pressure and diamonds

People naturally sort themselves into tribes. They form small groups with common interests. Left to their own devices, people will look for the differences in anyone they compete with. If a strong outside force appears, people will band together and look for similarities. They will see themsleves as a greater tribe with a united cause.

Pressure forms diamonds
It is strong external pressure that causes people to bond. People will untie against an outsider, a perceived foe. The United States are a good example. The Colonies declared independence from the British Empire in 1776. Each new State was protective of its own newly found sovereignty. They formed a Continental Congress to fight the British. In 1781 they united into a loose confederation. Problems were so great that the Convention formed to Amend the old compact instead wrote a new Constitution creating a stronger federation which began in 1789. The British continued attacking the new nation until the War of 1812.

For over 36 years, the United States were surrounded by empires and hostile native tribes. Those hostile forces forged the country into a single cooperating tribe.

Similar stories can be found in the rise of other tribes.

Failed unions
Any artificial attempt to form a bond or union will fail. A lack of external pressure will cause the breakup of the experiment into lesser tribes. Sometimes the breakup will be peaceful (Czechoslovakia, Soviet Union). More often it will be violent (Yugoslavia, Sudan).