China
I must admit that initially we did share the common opinion that China had never had its own, even partially independent and unique, tank development. To our great surprise and astonishment, when our Chinese partners brought up the idea of doing some research to prove that we were wrong - we just couldn't refuse.
The documents we got eventually are a true terra incognita even in China, not speaking of the rest of the world. Generally speaking, China is a closed (?) country, extremely reluctant when it comes to sharing its defence projects with others. The fact that we were able to obtain the information that allowed us to make up medium and heavy branches - is a great deal. It's rewarding to see how results of your hard work become "alive" in game. When our Chinese partners finish their research on SPGs and TDs, we will eagerly add those two missing branches as well.
That's how the Chinese tree was planted. True thing that initially it was intended for Chinese server only, however when we realized it all looked great, we had no other option, but to share our results with the rest of the world.