The speaker is dealing with the aftermath of war, and the title, "Post-traumatic," tells us the trauma lingers long after the fighting ends. The poem puts war in an ordinary, peaceful place: the supper table, where people usually feel safe and close. Instead of staying far away, the war has "found a root" there. That image suggests something that has dug in and grown, so the memory isn't passing but settled and alive in the speaker's daily life.
The last two lines turn war into an unwelcome guest with "no manners" and a "cruel music." Manners imply order and politeness, and the war has none. The "music" is an odd, unsettling choice. It might be sounds the speaker keeps hearing, like explosions or shouting, or it might be the way memory plays on a loop. The speaker's feeling seems to be unease, even helplessness, at being invaded in a place meant for comfort. The mood is quiet but tense, and the short lines make the intrusion feel sudden and hard to shake.