I thought I read somewhere that Frederick the Great praised George Washington in some way, and said so in one of my midterm exam essays. I can't find any reliable sources that confirm what I claimed though, so I hoped that this subreddit might be able to help.
OP, I'm not usually in the habit of doing other people's homework for them, but found an article about this very subject: http://www.jstor.org/stable/pdf/1833470.pdf
Notice that this article is from 1904, so please keep in mind that it may not reflect current scholarship on the subject. The general thrust of the article is that Frederick II did not have much in the way of strong feelings on the Americans or the American Revolution (Rebellion) itself, but was vaguely friendly toward them, insofar but he was firmly in favor of anything that made English foreign policy more difficult, and distracted English attention away from Hanover.
I'm not a historian. This is a letter from GW to Frederick from the National Archives. If I understood it correctly (I may not have) the 4th footnote mentions that the man who delivered this letter said that Frederick "express’d himself in terms of the warmest admiration of our President". If you can find more robust evidence that would probably be better, as this happened 11 years after the war, doesn't mention the war, and provides little detail. I may be incorrect but I think ideally if you are going to cite this and it's a college history class I would try to find the original article or letter that states that the delivery guy heard this rather than this letter with the footnotes.
https://founders.archives.gov/documents/Washington/05-15-02-0058
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