What was Tims "worst day at the war"?

From the text:

In the months after Ted Lavender died, there were many other bodies. I never shook hands--not that--but one afternoon I climbed a tree and threw down what was left of Curt Lemon. I watched my friend Kiowa sink into the muck along the Song Tra Bong. And in early July, after a battle in the mountains, I was assigned a six-man detail to police up the enemy KIAs. There were twenty-seven bodies altogether, and parts of several others. The dead were everywhere. Some lay in piles. Some lay alone. One, I remember, seemed to kneel. Another was bent from the waist over a small boulder, the top of his head on the ground, his arms rigid, the eyes squinting in concentration as if he were about to perform a handstand or somersault. It was my worst day of the war.