This is somewhat problematic, given that they share a 1,900-mile-long border. Each country fairly bristles with antagonism and nuclear weapons, so how they manage this unwanted relationship is a matter of life and death on a scale of tens of millions.

Border between USSR and China in 1969-1991 was 7,500 km long, and even now is 4,209 km (per internetz). Granted, USSR had lots of old tanks to reuse in fortifications. But building of helicopters started pretty much from scratch in reaction to falling out with China.

They came close to war again in 2001, and gunfire still breaks out sporadically along the border.

Gunfire just breaks out on its out. Clearly, ManBearPig is to blame.

The Pakistan military and the ISI had to turn on the very Taliban leaders they had trained and formed friendships with in the 1990s. The Taliban groups reacted with fury, seizing complete control of several regions in the tribal areas.

There may be some sort of an elephant in that room.