Why did Britain and Russia compete for influence in the Hindu Kush during the 19th century?

During the 19th century, the Hindu Kush became a focal point of the Great Game, a geopolitical rivalry between imperial Britain and tsarist Russia.12

The competition was driven by the following factors:

• Security of India: The British, operating from their base in India, were deeply concerned with securing the northern frontier. They viewed the mountain passes of the Hindu Kush as historically significant military routes that provided access to the northern plains of India and sought to prevent Russian penetration into the region.34
• Buffer Zone Strategy: Britain aimed to maintain Afghanistan as a buffer state to keep Russian influence at a distance. British officials often feared that local rulers were either hostile or too weak to resist Russian encroachment, leading them to intervene directly in Afghan affairs through the Anglo-Afghan Wars.34
• Imperial Expansion: As Russia expanded its influence across Central Asia, both powers became mutually alarmed as their frontiers drew closer. This led to a series of maneuvers to secure spheres of influence, ultimately resulting in the delimitation of Afghanistan's borders by the two powers.35