The débâcle of the Afghan civil war left a vacuum in the Hindu Kush area that concerned the British, who were well aware of the many times in history it had been employed as the invasion route to South Asia. In the early decades of the 19th century, it became clear to the British that the major threat to their interests in India would not come from the fragmented Afghan empire, the Iranians, or the French, but from the Russians, who had already begun a steady advance southward from the Caucasus winning decisive wars against the Ottoman Turks and Qajar Persians.