In 558, Khosrau I, Shah of Sassanid Persia, allied with the Göktürks to defeat the Hephthalites. The campaign was successful and the region north of the Oxus went to the Turks and the south came under Sassanid rule. However, in the 580's, the Turks once again commenced with their raids on the Silk Road and in 588, the Hephthalites, who were now part of the Western Turkic Khaganate, invaded the empire once more.
Bahram Chobin was chosen to lead an army against them. According to Shahbazi, Bahram's army consisted of 12,000 hand picked Savaran, Persia's elite soldiers. His army ambushed a large army of Turks and Hephthalites in April 588, at the battle of Hyrcanian rock, and again in 589, capturing Balkh. He then proceeded to cross the Oxus river and managed to repulse the Turkic Invasion and taking over Hephthalite territory that was occupied by the Turks.
It is reputed that an arrow shot by Bahram killed the Eastern Turkic Khagan, Bagha/Yabghu Qaghan, known as Ch'u-lo-hou by the Chinese .
Ferdowsi's Shahnameh (C.E. 1010) describes in legendary detail the dealings of Bahram Chubin and the Turkic "King Sawa" before and during the battle in which Bahram with his 12,000 kills Sawa