Explanation: Lytton made an offer of a favorable treaty to Sher Ali, but the Amir wanted friendship with both his powerful neighbors, Russia and British India, while keeping both at an arm’s length.

• Later, Sher Ali refused to keep a British envoy in Kabul while having earlier granted a similar concession to the Russians.
• Lytton was displeased, and when the Russians withdrew their envoy from Kabul, Lytton decided to invade Afghanistan.
• Sher Ali fled in face of the British invasion, and the Treaty of Gandamak (May 1879) was signed with Yakub Khan, the eldest son of Sher Ali.

Source: Spectrum Modern India