They were transported via Trans Atlantic trade system by boat. In the Atlantic Ocean
Europe and asia, i know for sure.
Slaves were crammed together.
I believe this is the answer:
It was feared that France would get allies (particularly Russian ones) so in order to prevent that Germany became Allies with 2 other countries to isolate France. This allowed Bismark, who had the idea, to continue with his plans.
Hope this helps.
