The reality of warfare
As this poem progresses, the soldier suddenly realizes what he is doing, becoming aware of the reality of the moment. He notices his uniform rubbing against his skin, and how heavy his rifle is. In essence, he has an epiphany about the dire reality of warfare, and the fact he is expected to kill other human beings. The absurdity of war is something Ted Hughes is commenting on through his description of the soldier.
Free Will
During the soldier's epiphany, he begins to wonder why he is doing what he is doing. He questions what external and forces are controlling his actions, manipulating him into killing other people. He describes these forces as being "cold clockwork," including the "stars and the nations." Here, he is referring to ideas like fate, or political forces.
Patriotism
The soldier shifts from a feeling of patriotism to a belief that war is inherently futile. This shift occurs as the soldier suddenly "awoke" on the battlefield, coming to a realization about the situation he is in. He notices the heavy rifle numbing his arm and the sweat on his chest like "molten iron." The soldier had previously shed a "patriotic tear," but he now begins to question the purpose of warfare.
