Before getting one answer from Hungarians in the Civil War, let's drop in on McClellan's Own Story, a compilation of writings by GBM's literary executor.
Mr. Seward's policy of making ours a "people's war," as he expressd it, by drumming up officers from all parts of the world, sometimes produced strange results and brought us rare specimens of the class vulgarly known as "hard cases." Most of the officers thus obtained had left their own armies for the armies' good, although there were honorable and admirable exceptions such as Stah[e]l, Willich, Rosencranz, Cesnola, and some others. Few were of the slightest use to us, and I think the reason why the German regiments so seldom turned out well was that their officers were so often men without character.But they kept coming.
Soon after Gen. Scott retired, I received a letter from the Hungarian Klapka informing me that he had been approached by some of Mr. Seward's agents to get him into our army, and saying that he thought it best to come to a direct understanding with with myself as to terms, etc. He said that he would require a bonus of $100,000 in cash and a salary of $25,000 per annum; that on his first arrival he would consent to serve as my chief of staff for a short time until he acquired the language, and that he would then take my place of general commanding-in-chief. He failed to state what provision he would make for me, that probably to depend upon the impression I made upon him.
I immediately took the letter to Mr. Lincoln, who was made very angry by it, and taking possession of the letter, said that he would see that I should not be troubled in that way again.
Cluseret - afterward Minister of War under the Commune - brought me a letter of introduction from Garibaldi, recommending him in the highest terms as a soldier, man of honor, etc. I did not like his appearance and declined his services; but without my knowledge or consent Stanton appointed him a colonel on my staff. I still declined to have anything to do with him, and he was sent to the Mountain Department, as chief of staff I think.McClellan goes on to mention two German ADCs he liked, taken on at the request of a Prussian minister, and his high opinion of the famous French princes and their uncle (as you would expect).
But what does all this mean? Seward's game here is not too obscure, as we shall see.
(Photo of by Alexander Gardner of what appears to be part of Hooker's staff, L-R: Maj. D.S. "Peter" Ludlow, Ulric Dahlgren (standing); LTC Joseph Dickinson, AAG (recumbent); Graf Zeppelin of the Prussian Army, and McClellan's Swedish ADC, Lieutenant Frederick Rosencrantz. This site says FR "successively served Burnside, Hooker and Meade in the same capacity. His brave and genial disposition made him a universal favorite."