Borders, boundaries, obstacles.

Entropy's response begs deeper questions and answers not within our capability.

Ok, given enough resources anything is possible. I submit that the requirements to effectively close the border are beyond our current capabilities much less Afghans. The Afghans can't even fund their own security forces, much less a huge, complex border security system.
The Maginot Line was built out of expedience, and a hopeless effort to substitute technology for manpower, and practical solutions.

Stable borders are part physical and part accepted and meaningful: Dividing one recognized place from another, or one people from another.

Having spent much of my young army life staring at East German watchtowers, I find it hard to believe that, in the Durand application, we could still be having a debate about building an Iron Curtain to force a division that is neither accepted nor definable by reasonable practice.

IMO, perhaps the best way to end the division would be to create it. First, we divide these two places by walls, dogs, mines, machine gun emplacements---essentially a huge public works project comparable to the Great Wall and visible from satellite.

During construction, we employ tens of thousands of contractors, builders, suppliers on both sides of the line, of necessity carving out new roads across the entire area for supplies, and worker encampments.

Do the math on the sheer amount of labor and logistics needed to man and control the checkpoints. That, of itself, creates links never imagined, and defies credibility that either the enfeebled Afghans or unconcerned Pakistanis would ever support, staff or pay for.

Assuming it is ever completed, we funnel all trade through a few key checkpoint Charlies while cutting off centuries old informal connections on both sides, forcing ancient towns, peoples and relations to either "find a new life" or find a new way through the obstacle.

Finally, when all is said and done, some other political consequence, perhaps, in part, driven by the wall itself, causes a political realignment in this haphazard and unnatural border. The result: Like Hitler retaking Rhineland, driving through the forest to Bastogne, or bypassing the Maginot, it becomes a very large paperweight.

Whose wall is this, after all?

Whose actual short-term objectives are going to be addressed by it?

We really should try to go a little beyond just making this stuff up. No?