Erwin Smith was the 13th commander of the Survey Corps. Discerning, intelligent, and widely respected, Erwin was an able commander. While he cared deeply for his men, he did not hesitate to sacrifice them for the good and prosperity of mankind, and his men proved more than willing to stake their lives at his order. During Erwin's career he developed the Long-Distance Enemy Scouting Formation, and due to uncertainty about his future, he later named Hange Zoë as his successor.
Erwin had a commanding presence, standing tall above most members of the Survey Corps, and had a quite muscular build with his blond hair kept neatly parted on the left side.
Erwin was a complex character, portrayed as serious, calculating, and always planning far in the future. While he trusted his men, he was the first to realize that there was a spy interfering with the Survey Corps, and was able to come up with a reasonable criteria to determine which of his soldiers to trust with vital information, and which to keep in the dark. An eloquent speaker, Erwin was able to sway many people, such as the military tribunal held to judge Eren and the trainees into choosing which recruitment branches to join.
Appearance: Erwin had a commanding presence, standing tall above most members of the Survey Corps, and had a quite muscular build with his blond hair kept neatly parted on the left side. Erwin always wore a calm and collected expression on his face, with his icy blue eyes being one of his most striking features.
Personality: Erwin was a complex character, portrayed as serious, calculating, and always planning far in the future. While he trusted his men, he was the first to realize that there was a spy interfering with the Survey Corps, and was able to come up with a reasonable criteria to determine which of his soldiers to trust with vital information, and which to keep in the dark.
History: As a child, Erwin was a curious and insightful individual who did not accept facts at face value. He asked why humanity had no memory of what happened before they lived within the Walls, because even if they had lost all their records, the first generation should have been able to teach their children.
Erwin Smith in the story: In the year 845, Erwin takes part in an expedition beyond Wall Maria. When the soldiers encounter a Titan, Erwin reports their distance from the Titan to Keith Shadis while the Corps splits up to engage the Titan. When the expedition returns, Shadis requests that Erwin take over as commander of the Survey Corps.
Source: Attack on Titan Wiki, available under CC BY-SA 3.0.