Doves are well-known symbols of peace. Although such symbolism is strongly associated with Christianity, the associations between doves and peace go back much further than this: in ancient Mesopotamia, doves were symbols of Inanna-Ishtar, the goddess of love, sexuality, and (perhaps surprisingly) war. Indeed, the ancient Greek word for ‘dove’, peristerá, may be derived from the Semitic peraḥ Ištar, meaning ‘bird of Ishtar’. We’ve written about Inanna, the subject of the oldest known epic poem, here.
Dove symbolism in Christianity
In Christianity, the dove is used symbolically in both the very first book of the Old Testament (the Book of Genesis) and the very last book of the New Testament (the Book of Revelation). In Genesis, following the Flood, Noah sends forth a dove from the ark, and the dove came back with an olive branch in its mouth: a sign that the waters had receded enough for an olive tree to grow. Since then, of course, doves and olive branches have been well-known symbols of peace – although, as we’ve already seen, doves had already attracted that association.
Curiously, the raven and the dove also feature in the earlier Epic of Gilgamesh, another pre-Homeric (and pre-Christian) work of literature 
from Babylonia. Utnapishtim releases a dove to find land, but it merely circles the area and returns. After the dove’s failures, he releases the raven, and when the bird doesn’t return, Utnapishtim concludes that it’s found land.
This is a reversal of what happens in the Biblical account of the Flood (in Genesis 8:6-12), where the raven is sent out first, then the dove:
And it came to pass at the end of forty days, that Noah opened the window of the ark which he had made: And he sent forth a raven, which went forth to and fro, until the waters were dried up from off the earth.
Also he sent forth a dove from him, to see if the waters were abated from off the face of the ground; But the dove found no rest for the sole of her foot, and she returned unto him into the ark, for the waters were on the face of the whole earth: then he put forth his hand, and took her, and pulled her in unto him into the ark.
And he stayed yet other seven days; and again he sent forth the dove out of the ark; And the dove came in to him in the evening; and, lo, in her mouth was an olive leaf pluckt off: so Noah knew that the waters were abated from off the earth.
And he stayed yet other seven days; and sent forth the dove; which returned not again unto him any more.
We have analysed the biblical story of the Flood in more detail, and corrected some of the misconceptions about it, here.
Dove symbolism in classical myth
But the dove is also found in other ancient belief systems: in classical Greek myth, for instance, doves were associated with Aphrodite, the goddess of love, and were thus associated with physical or erotic love, rather than some ‘purer’ love such as religious devotion.
In both Christian and pagan cultures, however, the dove tends to represent an important aspect of the human soul. As The Penguin Dictionary of Symbols (Penguin dictionaries) observes, it was perhaps the whiteness of the bird’s feathers, combined with its gentle cooing, which helped to create this association between doves and the human spirit. Of course, lovers are sometimes said to ‘coo’ sweet nothings at each other, so we can see how this association came about.
Dove symbolism in literature
In his obscure poem ‘The Phoenix and the Turtle’ (it’s been called the first published metaphysical poem), William Shakespeare writes about doves, as the title makes clear. Or rather, to our modern eyes, perhaps doesn’t make clear: many people assume the poem is about the mythical bird that could rise from the ashes of its own funeral pyre, and a slow-moving shelled reptile known for eating pizza in the sewers (a reference for any fans of the Teenage Mutant Ninja Turtles there).
But no: Shakespeare is writing about the turtle dove, describing the funeral for the Phoenix and Turtledove (which represent perfection and devoted love respectively):
Whereupon it made this threne
To the Phoenix and the Dove,
Co-supremes and stars of love,
As chorus to their tragic scene:
Beauty, truth, and rarity,
Grace in all simplicity,
Here enclos’d, in cinders lie.
Death is now the Phoenix’ nest,
And the Turtle’s loyal breast
To eternity doth rest,
Leaving no posterity:
’Twas not their infirmity,
It was married chastity.
Truth may seem but cannot be;
Beauty brag but ’tis not she;
Truth and beauty buried be.
To this urn let those repair
That are either true or fair;
For these dead birds sigh a prayer.
As the reference to the ‘Turtle’s loyal breast’ indicates, Shakespeare is drawing upon the centuries-old symbolism of doves as representatives of love and devotion.
This symbolism of the dove, linking it to peace and love, persisted even in the face of the horrific events of the twentieth century, and even during massive industrial warfare. In his 1917 poem ‘Insouciance’, the imagist poet Richard Aldington plays on this peace symbolism, writing that the poems he creates in the trenches fly away from him like ‘white-winged doves’. Doves are messengers of peace, but pigeons – which are, after all, related to doves – were literal messengers in the trenches. Messengers of war, we might say.
In the Second World War, another modernist poet, T. S. Eliot, wrote memorably of the air raids on London in his 1942 poem ‘Little Gidding’. Describing the German bomber plane as a ‘dove descending’ with ‘flame of incandescent terror’, Eliot combined the man-made plane – a symbol of death and terror – with the peaceful dove. In doing so, he drew upon the purifying symbolism of fire, and the idea that London – and perhaps Europe more widely – might rise from the rubble of the war and be remade (Eliot probably also hoped for a resurgence of Christianity, given his own beliefs and the strong religious connotations of the dove).