Dear Hiawatha of the Iroquois in Civ. 5. Don't frick with me

So last night I started playing Civilization 5 again. I was going to do a peaceful victory through economics or science as the Austrian Empire. Well for almost the entire game I was friends with everyone on the map, including countries that were at war with each other. My largest bordering neighbor was Germany and we stayed on really good terms. The problem started around 1800 with my southeastern neighbor, the Iroquois.

As the Austrian Empire you can go through a Diplomatic Marriage with city states, so the majority of the time, this is how I expanded my empire. Well, I bought a few that bordered the Iroquois, then settled one city on a small strip of land by the ocean so I could connect those cities with the rest of my empire. No big deal right? Well, the Iroquois had two cities (one settled and another was a city state they took over and were using as a puppet) that were cut off because of my new borders and an ally had told me that for some reason the Iroquois were plotting against me even though we had a declaration of friendship.

A few turns go by, and everything is fine. Then all of a sudden, Hiawatha denounces me for settling cities too aggressively. Then 5 turns later he starts threatening me saying that he and his allies are getting ready for war and that my days are numbered. So, by this time I have built several nuclear power plants, have a decent uranium supply and around 50,000 gold. I buy a few nukes that are within range of their capital then pay the French and Germans to declare war on them. Then after he threatens me again, I launch two nukes at his second largest city, take it over pretty easily then burn it to the ground. Then I launch two more at his capital and another at one of his smaller border cities. Needless to say, as soon as he could he was begging for mercy. Offered me one of his cities in exchange for peace.

So now I have another city, burned down one of his most productive cities, brought his capital to it's knees and now all of his farmland has nuclear fallout on it. Only bad thing now is that France is "guarded" about me.

Do. Not. frick. With. Me.

TL:DR version

Hiawatha threatened peaceful Austria. I nuked his second largest city then burned it down, almost burned his capital down and took one of his border cities.