The title of this novel is an interesting one. On the one hand, it refers to the emotional baggage the soldiers carry after their experiences on the battlefield, and on the other hand, it refers to the physical items the men carry. Often, these belongings tell us something about the character's personality.
O'Brien often describes the items his characters are carrying, giving us an insight into their personalities, desires, and needs. Ted Lavender, a young and inexperienced soldier, is a great example of this. He is unsurprisingly nervous and apprehensive before fighting, and therefore carries tranquilizers, marijuana, and extra ammunition. This indicates that Lavender is turning to medication to deal with his extreme anxiety. The fact that Lavender tries to prepare himself by bringing extra ammunition also indicates his fear of dying on the battlefield and his attempt to control this situation.
Another example is Norman Bowker, who notoriously carries around a dead thumb. This is actually quite a surprising thing for him to carry, as he is otherwise quite sympathetic and kind character. Ultimately, this item suggests that Bowker has become desensitized to the brutalities and horrors of war. Finally, Mitchell Sanders carries around some condoms, which represents his desire for physical intimacy. On some level, this also represents his need for an emotional connection and support.