What is the theme of "They"?

Siegfried Sassoon was a British poet known for writing
anti-war poetry of World War I. This poem is an example. There are two stanzas, written
in iambic pentameter, although with an irregular rhythm, and the rhyme scheme is:
ababcc, dedeff.

There is religious imagery in the poem. In
the first stanza, it says:

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The Bishop tells us: 'When the boys come back

'They will not be the same; for they'll have fought
'In a just
cause: they lead the last attack
'On Anti-Christ; their comrades' blood has
bought

This means that a
religious leader, the Bishop, has warned that when the soldiers come back from the war,
they will be changed. They will have faced death. The enemy is perceived as "the
Anti-Christ." This is a satiric comment indicating that the soldiers or their leaders
have depicted the enemy as evil to justify the war. The speaker in the first stanza is
an omniscient author.

In the second stanza, however, the
soldiers speak:

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'We're none of us the same!' the boys reply.

'For George lost both his legs; and Bill's stone
blind;

This stanza continues
to list the other horrors suffered by the soldiers, to which the Bishop
replies:

And
the Bishop said: 'The ways of God are
strange!'

The poet seems to
imply that in order to justify war, we have to vilify the enemy, turn the enemy into
"the Anti-Christ." The last line is a common statement used by religious leaders to
explain things that cannot be explained and in this poem, is an indictment against
war.