A few years ago I found the history of the 28th Infantry Division, and started to assemble the history pertaining to my Grandfather, who was in the 109th Regiment.  I never finished, but here is an excerpt:

On the night of 3 August 1918, the 109^th was ordered to take up pursuit of German forces who were retreating toward the Vesle River. They marched through that night and the next, rather than during the daytime. On the third night, they came under artillery fire. The Germans had crossed the river and taken up positions on the hills beyond, and from these heights, were shelling the roads over which the Americans had to advance. Most of the time the rain fell in torrents and so the nights were completely dark. At times, each man would grasp the end of the rifle belonging to the man in front so as not to lose contact. It was necessary to leave the roadway to avoid the shelling.

There was only one good road leading toward the Vesle river and the Germans knew the Americans would use it. The road was screened by a line of hills, and so the Germans put up an observation balloon and used it to good effect. As the 109^th rounded a corner, they came upon the bodies of almost an entire platoon from a preceding unit. This platoon had evidently felt safe from detection because of the screening hills, and marched down the road in a column while failing to notice the balloon just above the horizon. They had been annihilated. The 109^th left the road and kept out of sight of the balloon.

On 5 August, about 2 miles from the river, they dug in, still behind the screen of hills along the Vesle river. For the next several days, they held that position while enduring almost continuous artillery fire, including large quantities of mustard gas which was directed by German aircraft. There were heavy casualties. The enemy would often wait until mealtime to send a concentrated burst of fire, hoping to catch groups of men assembled for meals.

Each day the casualties continued until the 1^st Battalion was ordered to take a new position at the crest of the hill. After some time in plain view of the enemy, and even more casualties, they were permitted to withdraw back to their original position on the rear slope. To make matters worse, French artillery arrived a few hundred yards to their rear and drew even more fire than before. After losing many men and horses, the artillery withdrew. The men of the 109^th, however, were forced to stand fast and endure the shelling without a chance to fight back. The air was full of mustard gas and the stench of dead horses. This location received the name of “Death Valley.”