[Illustration: _The Union military telegraph corps strung more than 15,000 miles of wire during the war. In one year, the Northern armies kept the wires alive with nearly 1.8 million messages. Galvanic batteries transported by wagon furnished the electricity._] [Illustration: _Flag signals from natural elevations and signal towers could be seen as far as 20 miles on a clear day. Military information was often obtained by signalmen on both sides who copied each others flag messages and tapped telegraph lines._] [Illustration: _Balloon observation on the battlefield was made possible by the portable gas generator. Here Professor T.S.C. Lowe's balloon is inflated by mobile generators in front of Richmond in 1862._] [Illustration: _Dodging Confederate shells which whizzed dangerously close to the Intrepid, Professor Lowe telegraphed information on emplacements directly from his balloon and made sketches of the approach routes to Richmond._] [Illustration: _Faulty intelligence furnished by detective Allan Pinkerton (seated in rear) and his agents misled General George McClellan during the Peninsula Campaign. The Pinkerton organization was later replaced by a more efficient military intelligence bureau._] [Illustration: _A. D. Lytle, a Baton Rouge photographer, provided valuable intelligence to Confederate commanders. His photographs, like this one posed by the 1st Indiana Heavy Artillery, revealed the strength and condition of Union organizations._] [Illustration: _Artillerymen soften an objective for the infantry. Although field artillery was used extensively, it frightened and demoralized more men than it wounded. Only 20 per cent of the battle casualties can be attributed to the artillery._] [Illustration: _Assaults on fortified positions were costly, but here at Petersburg war-weary infantrymen await their turn for another charge against the Confederate works. Fourteen out of every hundred would fall._] [Illustration: _One of an estimated 584,000 Union and Confederate soldiers wounded during the war. Of this number, over 80,000 died._] [Illustration: _The Union ambulance corps provided one ambulance for every 150 men during the Wilderness Campaign. In one convoy of 813 ambulances, over 7,000 sick and wounded were transported to the hospital in Fredericksburg._] [Illustration: _Amputees, like these Union soldiers who survived the surgeon's scalpel, would never forget the traumatic ordeal. Most wounded went through surgery while fully conscious with but a little morphine, when available, to deaden the pain._] [Illustration: _A floating palace with bathrooms and laundry, the hospital ship_ Red Rover _gave many sick and wounded a better chance for life than they would have had in the crowded field hospitals._] [Illustration: _Carver Hospital, where thousands of stricken soldiers recovered. Walt Whitman and Louisa May Alcott nursed many sick and wounded in similar Washington hospitals._]