https://en.wikipedia.org/wiki/Felix_Salm-Salm
After the American Civil War was over, Salm-Salm offered his services to the Habsburg's Emperor Maximilian I of Mexico, and embarked for Mexico in February, 1866. Maximilian was actively promoting American soldiers to migrate to Mexico after the war to improve relations with the country. Salm-Salm was in an unusual position because he had fought for the Union while most of the Americans who moved to Mexico after the Civil War had fought for the Confederacy. By the summer he was appointed colonel and became the Emperor's aide-de-camp and chief of household. He was captured at Querétaro along with the emperor but not before he made a brave charge with his hussar cavalry in an attempt to save Maximilian from the surrounding Mexican Republican army under Benito Juárez. Together with the Emperor and his highest-ranking generals Tomás Mejía Camacho and Miguel Miramón he was sentenced to death by firing squad. Thanks to the tireless efforts of his wife (who had also tried to obtain a pardon for the Emperor Maximilian) he was pardoned by Juárez and released from custody in December 1867. During his captivity, he was promoted to the rank of brigadier general.