This paper discusses the Borderland Theory from the perspective of the Pak-Afghan border that gained great momentum in the post-9/11 episode. Borders play the most significant role in determining the relations between the bordering countries. The insurgents use it as a sanctuary after getting their nefarious designs fulfilled. For the very first time in the history of Pak-Afghan relations, Pakistan had to deploy security personnel on its western border in such a great number owing to the greater need for security from this border. Cross border infiltration had a great impact on the security paradigm of Pakistan. Some of the most noteworthy networks that were hotly pursued include the Neo-Taliban, Al-Qaeda and the Haqqani network. Border management, making joint security troops from both the countries for deployment along both sides of the border, while negotiation coupled with diplomacy will do a lot in eradicating terrorism and insurgency across both sides of the border.