Great Works: Soldier X, 1990 (142x70x37cm), Ed and Nancy Kienholz

Collection of the artist

It is not easy to create good political art for precisely the same reason that it is difficult to write emotionally convincing political poetry. If you know what you want to say before you say it, there is nothing left to be said. The rest is often raillery or sloganeering, or a mixture of the two. There has to be a space in the making process for the serendipitous, the intuitive, that groping forward in the dark until you eventually emerge into the light. And so it too often is with the art of war. No matter how sincere the unpremeditated act of spontaneous naked rage at the war machine or the machine politician, the art itself is too often skin-deep, and therefore lacks real emotional clout. There are exceptions, of course, and this week's choice is one of them.

Ed and Nancy Kienholz made work together for a period of almost 25 years. Only Ed's death in 1994 put an end to their collaborations. They hated the wastefulness and the immorality of war, and they made an entire series of anti-war sculptures. These works ranged from the brilliant simplicity of the work illustrated on this page to elaborate installations such as the Non-War Memorial of 1970, which consists of soldiers' uniforms messily and ungraciously strewn across the floor around a white plinth, on which a great book lies open full of thousands of photographs of yet more uniforms, all filled with dirt.

Their greatest anti-war piece, Soldier X, is art pared back to the uttermost. In fact, it is so simple that you wonder at this degree of seeming artlessness. And yet it could not be more searching. The wall-mounted piece consists of a battered soldier's helmet mounted on the end of an old, rusting, well-used spade. The empty helmet conceals – or perhaps it stands in for – the handle. At first you notice the rounded fullness of the emptiness of that helmet, mounted at the spade's far end. You take away the fleeting impression that this might be a sketchy, wholly featureless likeness – after all, it's nothing but a pole – of the thinnest of thin human bodies, one of those thin, hungry, care-worn bodies that might once have walked in step with one of Giacometti's walking men. The spade's end looks so far away. And yet the passage from one end of the spade to the other is as quick and painfully/painlessly easy as the passage from life to death.

And this is the meaning of the work – we register this quite quickly, and with some degree of shock. That long and slender wooden shaft is a straight, speeding route from life to death for the soldier. It is the simple contract that he has taken out. It is the inevitable meaning of his life as a soldier, to slip down that greasy pole, easy as winking. The piece is wall-mounted too, and this is important. If the foot of the spade were allowed to touch the floor, the piece would be robbed of some of its force as emblem. It would edge towards literal-mindedness.

You can also think of the sculpture as the simplest of simple genealogical trees – there has never been one quite so reduced in content as this one. It has just one line: there are no branchings off to ancestors, siblings or descendants. There is only this swift passage from war to death-in-war. And how poignant is the fact that the helmet is utterly empty, merely the shell of a battered old helmet, once owned by someone, and now co-opted into this sad work. You can imagine that the Kienholzes might once, at some stage in the making, have considered the possibility of filling this helmet with a head of sorts, made of plaster or some such material. How much better, and how much more effective, it is for being utterly empty of content, for being an empty shell of itself.

This emptiness also tells us several things, and these meanings come crowding in at us almost all at once as we look at it: it tells us that the this human machine who is part of the war machine is a cipher of sorts. His identity does not matter to those who have sent him on his mission. He is this remnant, an empty helmet. He is a body among all those thousands of anonymous others who were once out there on the battlefield – to do the filthy work assigned to him. And, yes, he is no longer there now, we know that, because this is evidently a memorial to a dead man. The fact that this is a memorial to an unknown solder, to a cipher called simply "X", is evident from the metal ring near the top of the shaft, marked with an x. The fact that he has been memorialised in this way both pleases and disgusts us simultaneously, pleased that his contribution should have been recognised in this way, and disgusted by the fact that he is a solder who has no name, that he may perhaps have been nothing other than parts of a person when he was found – or perhaps, more callously still, the x indicates that all who willingly play their part in the war machine are finally nothing, more or less, than that machine. Their identity is absorbed into a greater – or perhaps a lesser, depending upon your point of view – whole. The fact that this helmet is empty also makes us think about the fact that being seduced into going to war may have robbed soldier x of his powers of judgement, and even of his brains, that he may have been robbed of his skills as a decision maker by the slick posturings of the advertising man. Yes, he may have been seduced into believing that war is about manliness, the road to a new won prosperity, or that war is the proper forcing ground of pride. War makes a man of mere men. It also robs them of themselves by annihilating them at a stroke.

ABOUT THE ARTISTS

Edward Kienholz (1927-1994) and Nancy Kienholz (born 1943) created an extraordinary body of collaborative work, which mainly consisted of drawings, sculptures and large-scale sculptural installations. Their works were often created from the discarded detritus of all our lives – cardboard boxes, soup cans, pickings from the scrap yard. Ed became known as an artist in Los Angeles during the Beat era, and his early work is directly associated with the rise of Pop Art. But this is Pop Art with a social conscience and an unusual degree of political clout.