Lincoln Welcomes Prussian Prince Felix
Bismarck’s violent unification of the German States predated Lincoln’s, and certainly was more than a casual observer of an American president’s war upon his own people. German officers serving and gaining experience in the Northern army might later assist with Bismarck’s own war of unification.
Bernhard Thuersam, Chairman
North Carolina War Between the States Sesquicentennial Commission
"The Official Website of the North Carolina WBTS Sesquicentennial"
Lincoln Welcomes Prussian Prince Felix:
“With testimonials from the Crown Prince of Prussia to the Prussian minister resident in Washington,

[Prince Felix Sam-Salm] came to the United States, where he arrived sometime after the outbreak of war. As he knew no English, he wanted to serve with a German regiment, and [Colonel Ludwig] Blenker proved willing to accept him as his chief of staff.  At this time he was about thirty years of age…and wore a monocle with the traditional skill of a Prussian officer of the guard.
Through the good offices of the Prussian minister he secured an audience with President Lincoln. When told that his guest was a prince, Lincoln clapped him on the shoulder. “That won’t hurt you with us,” he said. The prince succeeded in getting on Blenker’s staff, which was famous as the “waiting room” for German officers. Somewhat later, his wife secured for him the post of regimental chief in the old Blenker regiment, the Eight New York, and then in the Sixty-eighth New York; finally, by the powerful influence she won for him a general’s title. Princess Salm-Salm was almost more distinguished than her husband, whom she even accompanied to the field…”
A brave but cautious officer, Salm-Salm found little opportunity to distinguish himself in his first campaign. Together with his regiment, he was mustered out of service in the spring of 1863 at the expiration of his two years enlistment. The accommodating governor, under the manipulation of the princess, appointed him colonel of the Sixty-eight New York, which proved practically a recruiting job, as the regiment mustered hardly enough men for a company. Again his wife used her wiles to induce important persons to assign men to the regiment until it muster a thousand men. In the course of her efforts she herself received a captain’s commission.
(Foreigners in the Union Army and Navy, Ella Lonn, LSU Press, 1951, pp. 292-294)