Explanation:

Among the various passes of Himalayas, the Khyber pass was the most frequently visited by the external invaders.
The Khyber Pass is a mountain pass connecting Afghanistan and Pakistan, cutting through the northeastern part of the Spin Ghar mountains. An integral part of the ancient Silk Road, it has long had significant cultural, economic, and geopolitical significance. Throughout history it has been an important trade route between Central Asia and the Indian Subcontinent and a strategic military location. The Khyber Pass is part of the Asian Highway 1 (AH1).