During the American Civil War, soldiers were faced with a number of ethical dilemmas. Lieber knew about some from his own European wartime experiences, as well as through his sons (two of whom fought for the Union, and another died fighting for the Confederacy near Williamsburg). While in St. Louis searching for one of his sons, who had been wounded at Fort Donelson, Lieber met Union General Henry Halleck, who had been a lawyer in civilian life and had published "International Law, or, Rules Regulating the Intercourse of States in Peace and War" in early 1861. As the war dragged on, the treatment of spies, guerrilla warriors, and civilian sympathizers became especially troublesome. So too was the treatment of escaped slaves, who were forbidden to be returned to their owners by an order of March 13, 1862. After Halleck became general-in-chief in July, 1862, he solicited Lieber's views. The professor responded with a report, "Guerilla Parties Considered With Reference to the Laws and Usages of War", and Halleck ordered 5,000 copies printed. That same summer, Lieber advised Secretary of War Edwin Stanton concerning the "military use of colored persons".