The speaker is waiting for someone to return, and the poem suggests this person is a soldier or veteran coming back from conflict. The imagery of "dark camps," "bullets," "embankments" and "deserted land" points to war, but it blurs into the speaker's own inner struggle. Triggers fly "around my head" like bullets, and fires burn "within my chest," so the fear and tension seem to live in the speaker as much as in the person who left.
The repeated line "marching home is what I do best" shifts by the end into "waiting is what I do best." That change is the heart of the poem. The speaker has become expert at something painful: standing by, "dressed and ready," while nights pass in restless worry. The mood is tense, weary and quietly bitter. There is love here, but also exhaustion, and a sense of being left rootless while life stays on hold.