A variety of poetic techniques in "Spring Offensive" present a portrait of the hopeless and destructive nature of war.
The title itself presents a bit of irony. Spring, after all, is a time of rebirth and growth. Readers might expect that a poem about war would be set in the winter, a time of death and decay. Yet the spring setting and the emphasis on the season's beauty lend a sense of unpredictability to the poem, which reflects the unpredictable and dissonant nature of war.
Also notice the use of caesura in the fourth stanza, which slows down the pace of the poem:
And instantly the whole sky burned
With fury against them; and soft sudden cups
Opened in thousands for their blood; and the green slopes
Chasmed and steepened sheer to infinite space.
The sharp divisions in the second and third lines excerpted here, marked by semicolons, represent the way the world is rent apart and "chasmed" in battle.
Imagery is woven throughout the poem, particularly to describe the peaceful natural setting where mankind engages in warfare:
Marvelling they stood, and watched the long grass swirled
By the May breeze, murmurous with wasp and midge,
The soldiers are in awe of the simplicities of nature, and the beauty of spring as it brings forth new life causes them to "marvel" at their landscape. This imagery, which is both visual and aural, accentuates the contrasting horrors of battle in the poem's later stanzas.
There are also examples of metaphor and simile:
For though the summer oozed into their veins
Summer, often symbolic of youth and comfort, is on the horizon for these soldiers. It attempts to "ooze" new life into their weary veins, infusing them with new vigor and courage. This figure is made explicit by a simile in the next line:
Like the injected drug for their bones’ pains,
The promise of summer is like a drug for the soldiers, a hopeful reprieve from their toils and labor.
Finally, there are numerous examples of alliteration throughout the poem, such as this aforementioned line from the second stanza:
By the May breeze, murmurous with wasp and midge
There is the alliteration of b sounds in "By" and "breeze" and of m sounds in "May," "murmurous," and "midge." The latter case of alliteration brings to life the very murmuring described.