Shikamaru was born on the autumnal equinox to Shikaku and Yoshino Nara of Konohagakure. The Nara clan were the keepers of a forest in which they raised deer and gathered medicinal supplies, notable for documenting generations' worth of medicine preparations and effects. Generally peace-loving (and lazy), their clan's secret ninjutsu techniques involved the manipulation of shadow. Shikamaru's childhood was unremarkable, with his greatest concern being how to avoid his overbearing mother. Because he slacked off in school so much, he just barely managed to graduate the Ninja Academy as the second-worst student next to Naruto Uzumaki. He was placed into Team 10 under the command of Asuma Sarutobi, along with his best friend Choji Akimichi and Ino Yamanaka.
Shortly after graduation, Shikamaru participated in the Chuunin Exams. Although he ended up forfeiting his match against Temari when he'd run out of chakra and realized that no strategy would win him that battle, the tactical skill that he displayed during the match ended up winning him the promotion anyhow, making him the only Genin who advanced to Chuunin that year.
During the exam's third phase, Konohagakure was attacked by Sunagakure and Otogakure. A sleeping genjutsu was cast over the audience in the stadium, and although Shikamaru was strong enough to dispel it, he continued to pretend to be asleep so that he would not be pulled into the fight. Unfortunately, he was found out and had to accompany Naruto and Sakura to find Sasuke, who had been chasing their enemy, Gaara. In a surprising moment of bravery, Shikamaru volunteered to stay behind to fight eight pursuing ninja so that Naruto and Sakura could go on ahead.
When Sasuke later abandoned Konoha to join Orochimaru, Shikamaru's first job as a Chuunin was to lead the team who would retrieve him. With Naruto and Choji as well as Neji Hyuuga and Kiba Inuzuka, Shikamaru formed a brilliant strategy of pursuit. However, the group was overpowered by the Sound Four, Orochimaru's team of specialized ninja. In the end they dispersed and were forced to fight individually against the four. Shikamaru's brilliance was not enough to save him, but Temari of the Sand, his former enemy, came to his rescue. He returned to Konoha ashamed and blaming himself for the near-fatal injuries of his team members. He nearly gave up his role as a Chuunin, but his father explained to him that, had his team been led by someone else, they probably would have died and Shikamaru would still be blaming himself for not helping them. When he got the news that his friends would recover fully, Shikamaru swore that he will be a better leader, for their sake.
After spending the next two and a half years working as an academy instructor and Chuunin Exam proctor, Shikamaru was assigned to the Niju Shotai, an organization devoted to tracking down and eliminating members of the criminal group Akatsuki from the Fire Country. Shikamaru, along with his sensei Asuma and two other teammates, ended up in battle with an apparently immortal Akatsuki member, Hidan. While Hidan and his sensei fought, Shikamaru realized that Hidan's ritual has made it so that Asuma suffered from every blow that Hidan inflicted upon himself. Using his shadow to manipulate Hidan, Shikamaru broke the jutsu and Asuma managed to decapitate the enemy. However, Hidan's partner, Kakuzu, reattached his head and Asuma was once again affected by the jutsu. Finally, Hidan succeeded in killing Shikamaru's sensei. The battle was then interrupted by the arrival of the other two Team 10 members, and the Akatsuki were called away to a meeting, leaving Shikamaru alive but devastated. He returned to Konoha to deliver the news of the death to his sensei's lover, Kurenai Yuhi, having sworn to Asuma in his dying moments that he would guard their unborn child with his life.
The mourning period was spent in preparation for revenge. He studied the properties of his sensei's knives and learned to infuse them with his chakra. Once mastered, he gathered the other two members of Asuma's team and set off to hunt the Akatsuki, with Kakashi Hatake to fill the role once held by Asuma as team leader. The knives played a key role in Shikamaru's strategy, and through some very clever trickery he managed to turn Hidan's ritual against his own partner, Kakuzu. Although Shikamaru was unable to kill Hidan, he did manage to explode the body into pieces and bury them deep in the forest of the Nara clan, where his still-living remains would be guarded for ages. Allies from Konoha, including Naruto, arrived to assist the group and Kakuzu was finally finished off as well.
Upon his return to Konoha, Shikamaru adopted a more serious attitude toward his work as a ninja than ever before, frequently called upon by the Hokage to assist in the most difficult tasks. When Akatsuki's attack on Konoha finally came, he was among the first to charge to the battle's front.