The flashbacks in Khaled Hosseini's The Kite Runner serve to establish protagonist Amir's central motivation in the story, as well as to draw connections between two generations of Afghani children.

In terms of the former purpose, these flashbacks show the reader why Amir feels compelled to return to Kabul. Hosseini describes in beautiful, vivid detail the childhood friendship between Amir and Hassan. He also details, however, the rape that Hassan suffered after their victory in the kite racing competition. Amir sees the rape unfold but doesn't step in to stop it. This betrayal is compounded when Amir lies to his father that Hassan stole from the family. Hassan, unwavering in his loyalty, confesses to a crime he didn't commit, and the two boys never see each other again.

This backstory explains the intense guilt that drives Amir to risk his life by returning to Afghanistan to save Hassan's son. It also highlights the pervasive nature of childhood sexual abuse in their culture, as both Hassan and his son suffer abuse from older men in their youth.

On a brighter note, however, the flashback draws parallels between the loyal characteristic of Hassan and his son. Both characters use a slingshot to save Amir from danger, and both characters gleefully chase after Amir's kite when it falls from the sky.

One of the most important purposes of beginning the novel The Kite Runner with flashbacks is that it pinpoints the one event that has had the biggest impact on Amir, the protagonist and narrator. It also gives the reader a glimpse into his formative years, providing an understanding about the actions he takes as an adult. At the same time, it enables Amir to introduce the key characters in the story in just a few words, although we do not learn much about any of them until later.

The novel opens in 2001 but starts with the narrator’s allusion to an incident that took place more than 25 years earlier. As he tells the reader,

I became what I am today at the age of twelve, on a frigid overcast day in the winter of 1975. I remember the precise moment, crouching behind a crumbling mud wall, peeking into the alley near the frozen creek.

The narrator does not describe the actual event to which he refers yet. However, by opening the book this way, he provides a tantalizing tease about what will come and also informs the reader about how important the event was that it has haunted him for more than a quarter of a century.

Just a few sentences later, he continues with the words that his friend, and his late father’s business partners, said to him when he called and asked Amir to return to Afghanistan:

Rahim Khan said just before he hung up, almost as an afterthought, “There is a way to be good again.”

With Rahim Khan's statement, the narrator lets the reader understand that he, Amir, feels that he has never been good. He holds himself responsible for whatever event it was that impacted his life some 26 years before. The narrator also then introduces the key characters in the story:

I looked up at those twin kites. I thought about Hassan. Thought about Baba. Ali. Kabul. I thought of the life I had lived until the winter of 1975 came and changed everything. And made me what I am today.

We ultimately learn that the narrator feels his entire life changed in one momentous moment back in Afghanistan when he failed to protect his friend and brother, Hassan.

Hosseini relies heavily on flashback not only to build suspense but also to support his theme of the past's immense effect upon the present.  At the beginning, Hosseini begins the novel in present day and then flashes back to Amir's childhood.  By using one-sentence statements such as "There is a way to be good again," the author causes the reader to want to keep reading to see what those statements suggest.  The flashbacks then explain the significance of the statements.

Amir is haunted by the past--he cannot be completely happy in the present or future until he goes back to redeem himself for past actions.