Wilfred Owen establishes assonance in the title and first line and then applies it consistently through the poem. It helps to keep in mind that assonance is oral and not related to spelling. It refers only to vowel sounds, identical or very similar. Repeated or very similar consonants are not part of the device but can enhance the similarity of sound.

Dulce et decorum est pro patria mori.

Bent double, like old beggars under sacks,

Knock-kneed, coughing like hags, we cursed through sludge....

Short E sound: dulce, et, decorum, est, bent, e in beggars.

Long O or related "aw" or "uh": decorum, pro, mori, double, old, a in beggars, under, coughing, cursed, sludge.

Note how several consonant sounds are interspersed in combination with those vowel sounds. This creates rhythm and flow without rhyme: Bent double, B E ... D Uh B L. Old beggars, O L D B E ...Uh....

Also consider this line:

And watch the white eyes writhing in his face....

Long I: white, eyes, writhing. Here, Owen uses only the same sound in three sequential syllables. He pairs it with T or Th. Although W starts three words, that usage is not alliteration because they are all pronounced differently.

As he approaches the end, he brings back and increases the use of sounds from the first lines.

If you could hear, at every jolt, the blood

Come gargling from the froth-corrupted lungs,

Obscene as cancer, bitter as the cud

Of vile, incurable sores on innocent tongues....

Two of the final assonances are actually a rhyme, "glory" and "mori," but they also feature the often-used "aw" sound.

When scanning a poem for assonance, the reader must "hear" the words because spelling is not a reliable guide for the way the words are pronounced.

In the first line of the poem, the pronunciation of the short "e" in "bent" and "beggars" is the same, as is the "u" sound in "double" and "under."

The long "e" in "kneed" and "we" creates assonance in line two.

In line eight, the side-by-side words "dropping softly" share the short "o" sound.

Line ten features short "i" sounds in the words "fitting" and "in."

Three long "i" sounds are found in line twelve in the words "like," "fire" and "lime."

In line thirteen, there are three short "i" sounds in "dim," "misty" and "thick."

The words "green sea" share a long "e" sound in line fourteen.

In line fifteen, "my," "my" and "sight" all feature a long "i" sound.

The repeated short "i" sound is heard in "guttering, choking, drowning" in line sixteen.

In line seventeen, the side-by-side words "you too" create assonance.