During the American Civil War, the British Government had maintained economic ties with the Confederate States and supplied them with arms and ammunition. In addition, Confederate agents had launched raids from Canada into the Northern states. Consequently, there were concerns that the United States may take military action against Canada after its victory over the Confederacy. These concerns were instrumental in hastening the unification of the British North American colonies for defence purposes.
The American Civil War was also the first conflict in which many modern weapons made their debut, and witnessed the large-scale use of railways and telegraphy in military operations. The high casualties incurred by both sides were a direct result of these developments. Quite simply military science had not yet developed tactics that allowed assaulting troops to overcome the effects of overwhelming firepower and gain their objectives. This contradiction remained throughout the 19th century and culminated in the horrendous killing fields that characterized warfare in the First World War. By the time of the Battle of Vimy Ridge in 1917 this conundrum was well on the way to being resolved. The Canadian Corps was a leader in the development of the new tactics.