I like to have TV shows playing as I work. They hold my attention in the background and allow me to work, it's an ADHD Band-Aid. Lately I've been watching back-to-back World War II documentaries.
The key factor in winning WWII was sacrifice. It was a war of attrition. NAZI Germany, militarist Japan and fascist Italy all had one thing in common. Their leaders each had a complete disregard for human life. They were more than willing to send their solders to die in battle. All the allies suffered loses but the war would have had a very different outcome if it were not also for Stalin's complete disregard for human life. Stalin sacrificed nine million of his own soldiers. After the war he executed soldiers who surrendered and even people who were caught alive living in territories taken by the enemy. About 20 million Russians died in WWII.
One could say Afghanistan of today is comparable to Germany at the end of WWII. There are obviously differences in culture, ideology and terrain. But, like Afghanistan today Germany's infrastructure at the end of the war was almost non-existent.
Ground combat troops in Afghanistan today would have to take and hold every city to stand a chance of succeeding if they are going to fight and attempt to win an insurgency. Let's assume we take and hold every city in Afghanistan. Then what? How long can we hold it? Who will surrender? Their ideology does not allow for the possibility of surrender. Are we also going to take and hold Pakistan? Or build a 1000 mile wall through the mountainous Afghan / Pakistan border?
The Russian's lost approximately 100,000 troops taking Berlin in the final days of WWII. They were fighting a severely depleted and weakened German army comprised mostly of teenagers and old men.
Wikipedia reports as of July the total number of troops in Afghanistan stood at 101,000 (68,000 US troops). Another 40,000 troops is obviously a politically motivated low ball figure. Are we planning to take and hold, not a city the size of Berlin, but a country twice the size of Germany with 140,000 troops, and prevent more insurgents joining the fight from Pakistan and elsewhere?
Not going to happen. We will literally bleed troop loses until we hit our pain threshold. That pain threshold for the Soviets was 15000. They quit after losing 15000 troops. About a million afghans were killed in that war. The Afghan's looked upon that as a victory. What is our pain threshold?
That kind of defeat in Afghanistan will make for a very angry public because people like to feel powerful, not weak. They will take it personally and feel the pain of defeat.
Fighting an insurgency is not a viable option. The Taliban will kick our asses just because they are prepared to die. Even after the atomic bomb was dropped on Japan a group of die hard Japanese officers stormed the Emperor's palace to prevent the tape of his surrender from being broadcast to the Japanese people.
Different cultures, same mentality.