In Tim O'Brien's The Things They Carried, there is no shortage of symbols: the talismans that many troops carry symbolize the hope for survival and luck; the enemy is a collective emblem of death; the country that sent them to South Vietnam is an emblem of good intentions gone wrong; the land itself becomes a symbol of a place where they do not belong—truly strangers in a strange land—the backside of the moon as far as Tim O'Brien and his platoon-mates are concerned.

Kiowa's death in the "swamp" is a particularly compelling symbol of the world turned upside down—one can make a reasonable argument that in addition to being yet another symbol of the futility of war, in O'Brien's vision of war in South Vietnam, the "shit field" becomes a kind of horrific womb, as well as a tomb, for Kiowa.

In a narrow sense, the sewage area for the village is a symbol of Lt. Cross's ineptitude as a leader. As he notes at the beginning of the episode:

Military matters meant nothing to him. He did not care one way or the other about the war, and he had no desire to command, and even after all these months in the bush, all the days and nights, even then he did not know enough to keep his men out of a shit field (161)

One of the primary duties of a combat leader is not to get his men killed through carelessness or bad decisions. In this case, Cross decides that this particular "blue feature," which is grunt speech for lakes, streams, and rivers on Army maps, is a logical resting place because water is easily accessible.

It apparently doesn't occur to Cross to be wary of the area, even though the villagers try to warn him and, in Vietnam, ignoring local knowledge usually leads to trouble. Cross's instincts are those of civilian—heavily armed and dressed in jungle fatigues, but still a civilian—and those instincts are not attuned even now to death in all its forms. The shit field will forever stay with Cross as a symbol of his failure.

When Kiowa's friend, identified as "the boy," brings mortar fire down on their heads by using a flashlight in flat terrain at night—almost a guarantee of trouble in the field—he is able to locate Kiowa, or what is left of him:

There was an arm and a wristwatch and part of a boot. There were bubbles where Kiowa's head should've been. He remembered grabbing the boot. He remembered pulling hard, but how the field seemed to pull back, like a tug-of-war he couldn't win, and how finally he had to whisper his friend's name and let go and watch the boot slide away (164)

Kiowa is no longer part of his friend's world because he has entered a kind of womb, forever protected from the dangers of life above the water. It is ironic that, in the world of war and South Vietnam, the "amniotic fluid" that now surrounds Kiowa is infused with excrement.

When Kiowa's platoon-mates finally recover Kiowa's body, it is described as a birth gone horribly wrong:

and after a moment Kiowa came sliding to the surface. A piece of his shoulder was missing; the arms and chest and face were cut up with shrapnel. He was covered with bluish green mud (167)

Kiowa was probably covered with placenta at his birth, but this new kind of "birth"—only available in South Vietnam—finds him covered in this war's version of placenta, in this case, "bluish green mud." The image, of course, is disturbing, but the war itself is disturbing in all its aspects—as O'Brien points out in "How to Tell a True War Story," war is irredeemably evil, and if anyone tells you about honor and glory, do not believe him.

On a symbolic level, then, the shit field is an emblem of personal failure, the hostility of the land itself, and, in a way befitting such a futile war, the symbol of a horrific kind of birth, which, ironically, is also death.

The field where Kiowa died also symbolizes the personal tragedy of millions of young American soldiers who gave their lives for a lost cause. The Vietnam War was lost due to political factors beyond the average soldier's control.

The swampy field symbolizes not just a loss of innocence (many American soldiers who fought were only 18-24 years old) but also a loss of hope. Many soldiers, like Kiowa, died serving their country in a foreign land. As an added tragedy, their families never recovered their bodies. Of the soldiers who died or were classified as missing-in-action in the Vietnam War, a few thousand remain unaccounted for today.

In the story, O'Brien relates that Kiowa's burial in the smelly, swampy field makes him one with the war. After the war, O'Brien receives a letter from Bowker, who admits that the war has destroyed his courage:

"The thing is," he wrote, "there's no place to go. Not just in this lousy little town. In general. My life, I mean. It's almost like I got killed over in Nam...Hard to describe. That night when Kiowa got wasted, I sort of sank down into the sewage with him . . . Feels like I'm still in deep shit."

Bowker relates in no uncertain terms his opinion of the war. To Bowker, the "stench" of the war (as symbolized by the swampy field) will never leave him. It follows him everywhere he goes. Essentially, the war resulted in two tragedies: the loss of young lives and (for surviving soldiers) the loss of hope and purpose. The memories of the dead and the travesties of war continue to haunt the living. O'Brien relates that Bowker hanged himself in a YMCA locker room in 1978.

So, the field symbolizes (among other things) the tragedy of lost innocence, hope, and young lives.

Water symbolism runs throughout The Things They Carried.  Water usually symbolizes baptism and renewal, but in O'Brien's novel it infects and kills.  But, years later, the Song Tra Bong, the river whose banks overflow and drowns Kiowa, is a place which triggers O'Brien's memories and inspires his stories.

Mary Anne survives swimming in the Song Tra Bong, whereas the innocent soldier, Kiowa, is swallowed by it.  Morty Phillips swallows a mouthful of it and dies, and Bowker, the professional soldier, kills himself because of its stench.  The Song Tra Bong is both a rite of passage and a sirens' song, and once baptized by it, one longs to return to it (to bury Kiowa's moccasins) and be tortured by it (Bowker's suicide).  And lest we not forget that O'Brien could have been saved from the whole Vietnam experience by a swim across a different river.

The shitfield where Kiowa died is a metaphor for the Vietnam War itself.  The land war in Asia is often referred to in similar terms as a "quagmire," which is literally a swamp, bog, marsh, or mire.  Figuratively, a "quagmire" is a mix-up, mess, predicament, quandary, confusion, sticky situation, or dilemma.  Personally, I like "shitfield" better than them all.  The Vietnam War stinks and kills, literally and figuratively.

So, the field symbolizes Vietnam, the quagmire of the Vietnam War, the death of Kiowa, the death of Tim's innocence, and the place where so many of Tim's memories are buried that he must return to it, with his daughter, so she too can tap into its source for storytelling.