I'm pretty sure its great britain
I think that the most controversial decision was to let Soviet Union have control over Eastern Europe (which did not initiate the war so there was no reason to "punish" it by taking way it's independence): the answer I find best is <span>C. the granting of Soviet authority over the nations of Eastern Europe</span>
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1) He was trying to Unite the country, no longer and south, but one country.
2)He abolished Slavery and needed the South to come to terms with this to enforce the laws.