http://en.wikipedia.org/wiki/Mohammed_Omar Soviet Invasion and radicalization
Omar fought as a guerilla with the Harakat-i Inqilab-i Islami faction of the anti-Soviet Mujahideen under the command of Nek Mohammad, and fought against the Najibullah regime between 1989 and 1992.
Thin but tall and strongly built, he was reportedly "a crack marksman who had destroyed many Soviet tanks during the Afghan War."
He was wounded four times and lost one eye in the battle of Jalalabad in 1989, which also marred his cheek and forehead. Taliban lore has it that, upon being wounded by a piece of shrapnel, Omar removed his own eye and sewed the eyelid shut. However, reports from a Red Cross facility near the Pakistan border indicate that Omar was treated there for the injury, where his eye was surgically removed.
After he was disabled, Omar may have studied and taught in a madrasah, or Islamic seminary, in the Pakistani border city of Quetta. He was reportedly a mullah at a village madrasah near the Afghan city of Kandahar.
Unlike most of the Afghan mujahideen, he speaks passable Arabic. He was "devoted to the lectures of Sheikh Abdullah Azzam. Piety, modesty, and courage were the main features of his personality," according to Lawrence Wright.
Forming the Taliban
Following the Soviet withdrawal from Afghanistan in 1989 and the collapse of the Communist regime in Kabul in 1992, his country fell into chaos as various mujahideen factions fought for control. Omar came to head a group of warriors known as the Taliban, or Students. His recruits came from the Qur'anic schools within Afghanistan and in the Afghan refugee camps across the border in Pakistan. They fought against the rampant corruption that had emerged in the civil war period and were initially welcomed by Afghans weary of warlord rule.
Reportedly, in early 1994, Omar led 30 men armed with 16 rifles to free two girls who had been kidnapped and raped by local commanders. His movement gained momentum through the year, and he quickly gathered recruits from Islamic schools. By November 1994, Omar's movement managed to capture the province of Kandahar and Herat in September 1995.