It is important to realise that in this novel Achebe spends a number of chapters describing and presenting traditional Igbo society to the reader before the white colonists arrive. The implication is clear: we are shown a fully developed and extremely complex society that is in no way backward, and that has existed for thousands of years by itself. This serves to destroy any myth that the white colonisers came to "save" or to help the "backward" people of Africa. However, the biggest single factor that resulted in the destruction of Igbo society was the arrival of these colonists. Note how this is described in allegorical terms in Chapter 7, with the arrival of the locusts:
And at last the locusts did descend. They settled on every tree and on every blade of grass; they settled on the roofs and covered the bare ground. Mighty tree branches broke away under them, and the whole country became the brown-earth color of the vast, hungry swarm.
The anaphora, created through the repetition of the phrase "they settled," combined with the repetition of the word "every," serve to demonstrate the all-consuming nature of the locusts, and through them the colonists. The way the locusts cover everything and even cause "mighty tree branches " to break because of their weight perfectly reflects the way in which the branches of traditional Igbo culture are broken through the arrival of these insects. The comparison, as the rest of the book demonstrates, is all too obvious. Just as "the whole country" is impacted by the arrival of the locusts, so too is life changed irrevocably by the arrival of the white colonists.