The "Friendly" Iroqouis and the Importance of Relationships

I made a big mistake about 100 years back in Civilization III. The Aztecs landed their ships on the shores of my territory and demanded gold, so of course I told them to take their empty threats elsewhere. Well it turns out that it wasn't an empty threat and they declared war on me. I thought that I had a chance of winning, but I was wrong; the Aztecs were far more advanced.
Enemies just kept on coming in waves and I had to focus all of my production on soldiers, and not on improving my civ (I chose guns over butter). My medieval soldiers were no match for the gunmen they sent over, so my army got depleted to the point where I didn't have enough soldiers to have one fortified in each of my cities. Because of that civil disorder broke out in every city and I was unable to produce anything. The ships kept coming and I knew it would only be a matter of time before my last soldiers perished.
All of the sudden and very much to my surprise, however, I got a message from the Iroqouis saying that they were willing to sign a mutual protection pact! And this was coming from the same civ that throughout the entire game had continuously prohibited my men from even setting foot in their territory! I had no idea what motivated the Iroqouis to want to help me in a war, but I really didn't care. All I knew was that my civilization was not going to fall to the Aztecs anymore, and it didn't. The Iroqouis obliterated the Aztecs for me.
Sounds good, right? Not exactly. As soon as I started celebrating after my new friends killed all of the Aztecs, I came to realize their malicious plan. I thought that the cities I lost to the Aztecs would again be a part of my civ after the Iroqouis cleared them out, but I was wrong: The Iroqouis took the cities for themselves! There was nothing I could have done about it without declaring war on them, which I knew I would not survive. I thought I had started a good relationship with the Iroqouis but their real intention was to gain more land and resources at the expense of my civ. For this they would pay dearly.
The Americans became my new best friends when only a few turns later they also offered me a mutual protection pact. I accepted and immediately declared war on the Iroqouis. Justice was served when the Americans came to my assistance and punished the Iroqouis for attacking me. A huge battle broke out with huge losses for all 3 civs. My civ eventually fell, but not before inflicting a lot of damage on the Iroqouis. My soldiers had no chance of winning in battle, but they fought bravely nonetheless. They were like Japanese kamakazi fighter pilots in World War II who committed suicide in order to kill more of their enemies. The war my soldiers fought was a war of principle, not a war to obtain resources. The Iroqouis stabbed me in the back and I got revenge. Since my plan didn't work out, I did everything in my power to make it as difficult as possible for theirs to work. If they had not cheated me I would have helped them in the future, but they were disloyal and had to be taught a lesson.
In order to be successful in a global economy it is essential to have positive international relations with other countries. The Iroqouis hurt their ability to trade with other civs when they cheated me because afterwards other civs agreed to enter into trade embargos against them with my civ. Without the ability to trade, production possibilities decrease because comparative advantages can't be realized. Forgoing beneficial trade is an opportunity cost that is hurtful to any economy. This was the price that the Iroqouis had to pay for not being trustworthy. Their conquest strategy would give them many immediate benefits, but in the long term they would suffer from not being able to trade.