In retrospect, I should have expected it. For the whole game, you had been aggressively militaristic. You conquered several city-states and the Aztecs and Persians. But I thought you liked me. We had always been friendly in our dealings. But no, you attacked me, invoking your need for "living space".
I don't like war. In fact, I hate it. I rarely declare war on others, and when others force me, I'm usually only trying to make them stop. That was what I was thinking when you took over Rostov. I would take it back, and give you whatever gold or resources you wanted to stop the invasion.
But you didn't stop there. No, you couldn't. You burned Rostov to the fucking ground, killing every last man, woman and child. Not only that, you conquered Brussels, my longest and closest ally. Russia protects her smaller allies, and for these atrocities, we shall not rest. There shall be no peace as long as we both exist.
You may have legions far larger than mine. But I am generations ahead of your technology. Your piddly little janissaries will scream as they are crushed under the treads of my tanks, and I am, as we speak researching atomic theory. I am not afraid of nuclear winter, and you will be able to offer no counter-attack, or mutually assured destruction.
Mark my words: I will not rest until each and every one of your cities is a ruined, radioactive crater, marring the face of this planet.