What is the formal structure of "Dulce et Decorum Est" by Wilfred Owen?

This poem can also be viewed as two sonnets. The first two stanzas, one of eight lines, an octave, and one of six, a sestet,could be seen loosely as a Petrarchan (Italian) sonnet though not in classical form as Owen does not strictly adhere to that rhyme scheme. The second portion of the poem is similar to a Shakespearean (English) sonnet, which consists of three quatrains (four line stanzas) and one couplet (two line stanza),though the stanzas are not broken into visible quatrains, but instead two stanzas, one of two lines and one of twelve lines.This may be one interesting way to look at this poem's structure.