In early April 2008, Kyle’s unit conducts a foot patrol into Sadr City, Baghdad. When they prepare to breach a house, an Iraqi man alerts insurgents. A grenade explodes as Kyle enters the building and, as the unit retreats under fire a massive explosive detonates nearby. A bullet strikes Kyle’s helmet, knocking his night-vision device backward and making him think he has been blinded. He pulls the helmet forward, restoring his vision. Another round hits his body armor, knocking him down. The experience shatters his sense of invincibility.

Kyle details how his fourth deployment began a month earlier in al-Qa’im, western Iraq, on a relatively uneventful assignment until his chief informed him he was selected for a special task unit in Baghdad. At Al Asad Airbase, he learns the mission involves Sadr City, stronghold of Muqtada al-Sadr’s Mahdi Army militia. A 30-man unit of elite SEAL snipers and JTACs (specialist air support personnel) will provide overwatch for Army engineers building a defensive wall to stop rocket attacks on Baghdad’s Green Zone. Against the SEALs’ advice, command orders them to enter Sadr City on foot at night, believing they can sneak in undetected. This caused the ambush Kyle describes. Army vehicles arrive with overwhelming firepower, rescuing the trapped SEALs.

Two days later, the SEALs return to establish positions in a multi-story building called the banana factory. Kyle kills an insurgent with an AK-47 at 40 yards, and another who appears with a rocket. When a child runs out to retrieve the launcher, Kyle holds fire. He records seven confirmed kills that day at relatively close ranges. He begins giving prime positions to other snipers but continues to engage targets, including three insurgents who appear just 15 yards away.

The fighting intensifies whenever they reach an intersection. Kyle considers Sadr City the most intense combat he experienced. Army intelligence intercepts insurgent communications confirming the SEALs are killing combatants, countering Iraqi government claims of civilian casualties. During one extraction, Kyle realizes he has left his sniper rifle behind and runs back with his officer to retrieve it moments before insurgents arrive. After a month of heavy fighting and insurgent losses, the wall nears completion and attacks dwindle. Muqtada al-Sadr declares a ceasefire and negotiates with the Iraqi government.

The unit is reassigned to target explosives-makers in rural villages near Baghdad, working with the Army’s 4-10 Mountain Division. Kyle notes tactical differences between Army snipers (who use spotters) and SEALs (who move in large numbers to provoke fights). During one mission, point man Tommy leads them through a hidden sewage pool; he falls in completely and becomes violently ill. Kyle spends two to three months in the villages, making more than 20 confirmed kills. The SEALs are frustrated when forced to release a suspected insurgent due to insufficient evidence. From a house on a village’s edge, Kyle spots a man 2,100 yards away, launching a rocket at a passing US convoy. He takes a long-distance shot and kills the target, his longest confirmed kill in Iraq. A firefight erupts, forcing them to run across an open soccer field under fire to reach rescue vehicles.

Kyle rejoins Delta Platoon in Rawah for routine desert patrols. His chief informs him he has been promoted to chief petty officer. Kyle reflects on the Navy’s flawed testing system that requires SEALs to test in their original job specialties and notes that Chief Primo’s intervention helped Kyle to get promoted. On routine patrols, Kyle cannot relax. He constantly relives being shot in Sadr City, suffers insomnia and extreme anxiety, and his blood pressure spikes dangerously. Feeling physically and mentally overwhelmed, he seeks medical help. Given the lack of missions and his condition, he agrees to return home early in late August.

Kyle leaves Iraq feeling that he is abandoning his teammates. He keeps his health issues to himself, feeling ashamed. In San Diego, a sleeping pill causes a blackout during which he works out and drives to base with no memory of events. He participates in a virtual reality study on combat stress. His vital signs drop during simulated firefights but spike during peaceful moments, the opposite of normal responses. A simulated scene of a Marine with a severe abdominal wound triggers memories of the dying Marine he held in Fallujah. Kyle reflects that he is haunted by those he could not save, not those he killed.

As his enlistment ends, Kyle struggles with leaving the Navy. Taya tells him their son needs a father and that she will move away to be near her own father if Kyle reenlists. The Navy offers him a recruiter position in Texas that would allow regular home hours. Kyle extends his enlistment twice while waiting, but the assignment never materializes. Feeling misled, Kyle finalizes his discharge.

Kyle and Ryan Job remain close. Ryan accomplishes remarkable feats despite blindness, including climbing mountains and competing in a triathlon. In 2010, Ryan dies from complications during follow-up surgery, shortly before his daughter is born. Kyle mentions Marc Lee’s mother, Debbie, who founded America’s Mighty Warriors to support veterans. He expresses profound, ongoing grief at the loss of his colleagues.

Kyle and former British Army sniper Mark Spicer develop plans for a tactical training company. Through investor J. Kyle Bass, they secure financing and co-found Craft International with partners Bo French and Steven Young. The company’s logo and slogan honor Ryan Job. Two days after his November 4 discharge, Kyle moves to Texas. Taya remains in San Diego to sell their house. The family visits Texas for Christmas, and Kyle asks Taya to return to San Diego alone while he keeps the children with him, with help from his parents. He cherishes time with his kids and notes that he began teaching his son gun safety at age two.

Kyle struggles with the civilian transition, feeling resentment and missing the SEALs. He falls into depression and drinks heavily. After totaling his truck in an accident but walking away unharmed, he begins accepting his responsibilities. He becomes involved in veteran charity work, collaborating with Marcus Luttrell’s Lone Survivor Foundation and Rick Kell and David Feherty’s organizations to provide hunting and shooting retreats for wounded warriors. He emphasizes veterans need respect and opportunities, not sympathy or handouts. Kyle concludes that being a husband and father has become his primary identity, replacing his identity as a SEAL.

Taya reflects on their relationship’s evolution, acknowledging the war’s difficult changes but affirming their love has matured. She buys Kyle a tungsten wedding ring with crusader crosses. Both express feeling loved and prioritized.

Kyle reflects that war permanently changed him, forcing him to accept death. As a Christian, he believes God will not hold his wartime kills against him, maintaining that everyone he shot was evil and deserved to die. His only regrets are for American lives he could not save. He thinks that war’s biggest impact was changing his perspective, making everyday civilian problems seem insignificant.