exposed to attack by mining.
These underground defenses included, besides the necessary pits, over two and one-half miles of drifts or tunnels.
In addition to the countermining at Petersburg
, the engineer troops were used to strengthen the fortifications and to build a branch railroad to facilitate the delivery of supplies.
During the investment of Richmond
, two pontoon bridges were maintained across the Appomattox River
, and one across the James
at Chaffin's Bluff; and additional pontoon trains were provided in case they should be needed.
Anticipating the necessity for the abandonment of Richmond
, General Lee
, during the winter of 1864-65, required the engineer troops to rebuild Bevill's Bridge over the Appomattox River
west of Petersburg
, and to send a pontoon bridge to the Staunton River
in Charlotte County
The engineer troops also prepared a map showing the routes to the different crossings of the Appomattox River
, to be used whenever the army should be withdrawn from Richmond
This map has since been lithographed by the United States Government.
In March, 1865, when the right of General Lee
's position was seriously threatened, engineer troops strengthened the defenses at Hatcher's Run
; but the main body of them served in the trenches in place of the infantry withdrawn to extend still further westward a line which was already more than thirty miles in length.
The Confederate reverse at Five Forks
, which cut off a part of Lee
's army from Petersburg
and forced it to retire to the north side of the Appomattox River
, was closely followed by the loss of a part of the entrenchments before that city, and this necessitated an interior line of defense, pending the withdrawal of the main body of General Lee
's army to the north side of the Appomattox River
This new line of breastworks was thrown up hurriedly, in part by the engineer troops, but chiefly by negro laborers.
This was probably the only time