From 1807, when the armies of Tsar Alexander I reached its northern borders, Afghanistan became an uneasy neutral zone between the Russian and the British Indian empires around which ‘the Great Game’ was played. The British launched three military interventions—in 1838–42, 1878–81, and 1919–21. None was successful. The first Afghan War against Dost Mohammed saw a British expeditionary force capture the capital, Kabul. However, surrounding tribes forced a desperate retreat through mountainous country and only one member of the original army of 16,000 lived to cross the Khyber pass back into India. The second war was precipitated by Lord Lytton's forward policies, which subsequently were repudiated by Gladstone's incoming 1880 government. The third war arose when Habibullah Khan demanded recognition by the British of the absolute independence of his kingdom. British arms, once more, found the Afghan terrain and peoples intractable. Afghanistan's sovereignty at international law was formally recognized on 21 November 1921. A fourth and unexpected intervention in Afghanistan began in 2001 when the Americans, with British assistance, drove out the Taliban as part of their campaign against international terrorism. But the struggle proved protracted and difficult.