One of the civilization was way ahead of me in term of tech.
Fortunatly I had a large empire, able to produce a lot of units, and this civilization was rater small.
So I sent loads of units on this civilization to take one city. Countless units died, but in the end I was able to take over the city and gain one tech.
What I did later was a bit of a cheat, but it worked. I removed all my units from the city, let the other civilization retake it, reconquered it the next turn and got another new tech.
I did this for a few turns, and presto, I was on par with the other civilization in term of technology. Then, it was game over for all the other civilizations as I was also the biggest producer in term of industry.
As for the capital, I did the trick to make a raid on it in another game. The motivation was a little different however. They were getting really close to launching to Alpha Centauri, taking their capital destroyed their spaceship. And I was able to win.
I also remember playing the game way past its end (something like year 3000 or 4000). It was quite funny, because of global warming, all the terrains were converted to swamps or deserts.
It might have been in civ 2, but I think I once lots of nukes just to see if I could terraform the deserts into arable land through global warming.
Turns out I could, but it would make so much damage to the rest of the land or infrastructure that just sending loads of engineers/settlers to do the transformation was more economical.
Good times!
I really enjoyed starting a civil war by capturing another civilization's capital city. There was one game where I was in the Americas and the Zulus (always crazily warlike and expansionist) had conquered the rest of the world. It looked like they were going to overwhelm me.
So I parked an aircraft carrier and a bunch of transports off of southern Africa and captured their capital city with a surprise attack by overwhelming forces. The entire Zulu empire immediately started a civil war, with half of it becoming the Egyptians. I was unaware of the civil war feature when I did so (wasn't documented in the manual), and it really improved my opinion of the game. I ended up winning because the new Egyptian civilization and the Zulu civilization were too busy fighting each other to send enough against my forces.
The technology capturing feature was great too. I was playing in the Americas one time, and I was hopelessly behind the Chinese. I had musketeers and cannons, while they had tanks. I launched a surprise attack with all the forces I could muster and captured a few of their cities, getting technologies such as the automobile by doing so. I was then able to produce tanks, and ended up modernizing myself by capturing more cities and stealing technology.
I absolutely loved that game.