As conventional warfare turned rapidly against the Confederate States of America in early 1864, the Confederate government launched a formal campaign of behind-the-lines insurrection, subversion, and sabotage in the North. Using Toronto-based military personnel and pro-Southern Northern sympathizers known as copperheads, it sought to free rebel prisoners of war, create a Confederate Army of the North for traditional operations, seize state governments, and carry out destructive acts to hinder the Union war effort. This effort, centered especially on Illinois, Indiana, and Ohio along the Canadian frontier, became known as the Northwest Conspiracy. In September 1864, after the failed Chicago Revolt Operation during the Democratic Party's National Convention, operatives of the Confederate Canadian Squadron under Captain Thomas Henry Hines and Captain John B. Castleman withdrew to Mattoon and Marshall, Illinois. In central Illinois, these operators included Confederate officers, former cavalrymen, and escaped prisoners of war recruited by Hines for clandestine work, and while based in Mattoon and Marshall they carried out numerous successful missions, including the destruction of federal warehouses in Mattoon and river steamers on the St. Louis waterfront. The Canadian Squadron's activities provided covert tactical concepts later adhered to by the United States Office of Strategic Services during World War II and by its successor, the U.S. Central Intelligence Agency.