The speaker of "Peacenik" imagines a deliberately silly plan for ending war: tell the navy to get a dolphin drunk and marry her. Dolphins are sometimes used by navies, so the joke has a sharp edge. The speaker takes a military resource and pictures it turned into a wedding guest, or a bride, in place of battle. The idea is ridiculous, and the poem seems to know it.
The ending shifts the tone. After the fantasy comes a quieter line: the speaker "resolve[s] again" to see home and bed. The word "again" suggests this is a repeated promise, as if the speaker keeps being pulled toward big, helpless worries and keeps retreating to something small and real. The mood is wry but tired. The humor feels like a way of coping with a problem too large to fix, and the closing wish for rest and comfort sounds both sincere and a little defeated.