<p>Lowe had three balloons on station: 'Washington', 'Intrepid' and 'Constitution'. Observations made routinely from them convinced him that Confederate forces were massing for an attack on Heintzelman's force across the river. In later years, Lowe included this description of the events of the battle in his unpublished memoirs: "From eleven o 'clock until dark, on the 29th of May, the enemy commenced to concentrate their forces in front of Fair Oaks, moving on roads entirely out of sight of our pickets, and concealing themselves as much as possible in and behind woods where none of their movements could be seen except from the balloon...
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<p>"On the 31st of May, at noon, I ascended at Mechanicsville and discovered bodies of the enemy and trains of wagons moving from Richmond toward Fair Oaks. I remained in the air watching their movements until nearly two o'clock when I saw the enemy form in line of battle, and cannonading immediately commenced.
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<p>"I made an observation that showed that the Confederates were marching to attack our troops on the right bank of Chickahominy before the completion of the bridge would permit those on the left bank to join them. This would mean the destruction of our army. I descended immediately and sent off the most important dispatch of any during my whole experience in the military service."
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<p>Lowe advised McClellan's staff of the situation: Confederate troops were in position, and wagon trains and artillery were moving up rapidly to engage Hentzelman's force. The armies clashed and, within minutes, heavy smoke from the volleys of rifle and cannon fire drifted above the battleground, making observations difficult. But it seemed that the Union line was holding. Time dragged; across the river, two divisions of Union troops were waiting in reserve. Finally, late in the afternoon, their orders arrived, and they began to cross on a floating log bridge. The noise of battle urged them on. The Union line retreated under the fierce pressure of the rebel assault, and was holding tenaciously to its second line of defense. The fresh Union troops hit the field at a run, shouting and firing; they pressed the attack, forcing the grey-clad troops into retreat. And the Union command staff, inexperienced and lacking any real brilliance in tactics, thought that was the end of it. Tomorrow the Union forces could continue their march southward, and in a few weeks the rag-tag armies of secession would be crushed decisively. The Rebs were retreating; they'd keep going until they were in Richmond. Lowe made one more ascent on that busy day, the huge balloon lifting him into the night sky, giving him a vantage point to observe lights across the river where the Confederates had held the field. There were far too many, he thought, for stretcher bearers and doctors. There were enough for a whole army. His first ascent the following morning confirmed his suspicions. The Confederates had held their positions after falling back, and were readying a second attack. Worse, Lowe could see reinforcements on the road up from Richmond, infantry and cavalry columns kicking up the dust against the pale morning light. It was a major Confederate effort that almost emptied Richmond of its defenders, and without Lowe's reports it would have caught the Union armies unprepared. The war between the states might well have ended right there on the banks of the flooded Chickahominy river. The two armies met again in a charnelhouse that turned field and forest into plains of the dead. Close combat and point-blank range dropped Johnny Reb and Billy Yank within arm's reach of each other. Through it all, Lowe kept 'Washington' and 'Intrepid' in the air, observing and reporting four times each hour to ground headquarters, enabling them to update their battle intelligence and redeploy troops.
