In this chapter, there's a sort of hodgepodge of events which set up for events to come in Chapter 7.
So, war comes to Afghanistan. It's July 17, 1973. Ali, Hassan, and Amir huddle together in the living room while gunfire and explosions thunder around them until morning. Baba shows up safe and sound at sunrise, having made it through or around the blocked roads.
Amir and Hassan decide to go climb their pomegranate tree. (In an earlier chapter, they carved their names in this tree.) On their way there, trouble strikes in the form of Assef, Wali, and Kamal, three neighborhood boys.
We learn a little about Assef: he uses brass knuckles, has a German mother, and is known for his meanness. Oh yeah, he also torments Ali a lot.
Assef starts talking some nonsense about the new leader Daoud Khan and how he's going to have a man-to-man talk with Daoud Khan next time Daoud is over at his house. Assef will tell him about Hitler and ethnic cleansing and how Afghanistan needs to get rid of the Hazaras. Amir wants to get out of there. (Don't forget Hassan is a Hazara.) Assef, like always, has other ideas: he takes his brass knuckles out of his pocket.
Hassan comes to the rescue. In a single movement, he picks up a rock, takes his slingshot out of his back pocket, places the rock in the cup, pulls back the elastic band, and aims it at Assef's left eye. Kobe Bryant probably isn't this coordinated.
Assef and his crew back off.
It's Hassan's birthday. Baba always gets Hassan something special, like a Clint Eastwood cowboy hat or train set. Think awesome toys instead of reindeer sweaters. This year, Baba presents one Dr. Kumar, from New Delhi, to Hassan. What the deuce? Dr. Kumar performs surgery on Hassan, correcting his harelip.
Amir tells us the scar from the surgery heals by the following winter. At which time Hassan stops smiling. (Foreshadowing…)