What is the theme of "Anthem for doomed youth"? How does the poem view war?

It is clear that this is one of many World War I poems
that represent a crushing indictment on the whole military enterprise, presenting
another image than one that views war as something noble and heroic. Things to notice in
this excellent poem are the strident, angry (at times almost sarcastic) tone that
presents a picture of war that is anything but glorious. Also note the choice of words
and figurative language that is used to underline this message and
tone.

Note how the poem
begins:

What
passing-bells for these who die as
cattle?

Owen here presents
the harsh reality of soldier-life. They do not die a glorious, heroic death, but here he
uses a simile to reveal the real way most soldiers meet their death--as if they were
cattle being herded towards a slaughterhouse.

What is also
interesting is how Owen uses the sounds of war to make their funeral service. There are
lots of examples of onomatopoeia here, for example:

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Nor any voice of mourning save the
choirs--
The shrill, demented choirs of wailing
shells

Note here how Owen
makes the "wailing shells" into the only choir that will remember the lives of these
dying soldiers. 

Consider too how the poem
ends:

And each
slow dusk a drawing down of
blinds.

Clearly the onset of
dusk is symbolic, as is the drawing down of blinds: the dusk represents the dying of so
many soldiers, and during this time, houses would draw down their blinds to show that
someone had died in that household. This then is the only remembrance for their wasted
lives--and it is clear that the theme of this poem is to speak out against the horror of
war.