During the Civil War, many Americans were mindful of the British attack on the nation's capital during the War of 1812 that resulted in the burning of the White House and U.S. Capitol. Americans were acutely aware that control of the capital city could define a nation. Washington, D.C., therefore, played a significant part in the Union strategy and became a political symbol of the Union during these turbulent years.
The Defenses of Washington were a tangible expression of the Union cause. Northern leaders firmly held on to the belief that if Washington fell into Confederate hands other countries would recognize the South and back it with defensive troops and financial support. The military leaders of the south believed this as well.
This sentiment was summed up by John G. Barnard, supervisor of the construction of the defense system encircling Washington, D.C. The following excerpt is from his report, A Report of the Defenses of Washington, to the Chief Engineers:
It is scarcely necessary to dwell upon the necessity, in the civil war through which our country has just passed, of holding and defending Washington. In a war of the nation—united and patriotic—with a foreign power, conquest by the enemy of the seat of government, through it might be a disaster and even a disgrace, would have little influence upon the issues of contest. In the recent civil war, on the contrary, the rebel flag flying from the dome of the Capitol would have been the signal ‘recognition’ by those foreign powers whose open influence and active agency would be too willingly thrown, with whatever plausible pretext, into the scale of dismemberment to become almost decisive of the event. That the preservation of the national cause should have thus identified with the continuous tenure of a city situated as is Washington, upon the very boundary to the most powerful and energetic of the rebellious States, and surrounded by the territory of another State only restrained from open rebellion by the heavy pressure of armed force, was one of the chief embarrassments of the Government in the prosecution of the War.