The Taliban contested the US that entire time within Afghanistan and were seizing and controlling large portions of the countryside to use as bases, all right under the US's nose.
lmao no they didn't, they kept the majority of their command, control, and logistics base in Pakistan, where the US couldn't reach them. You think it's an accident that Osama Bin Laden was caught a stone's throw from Pakistan's major military academy? When you have an enemy who's vital rear areas can never be assailed, even if you vaporize his army he'll have all the time in the world to just build another one.
This
exact same thing happened in Korea, Iraq, and Vietnam. Korea is especially notable because the Chinese Army actually joined the war
directly against America. With Iraq, the "civil war" was mostly foreign fighters trained and equipped in Iran. Iran even mass-produced off-road EFP mines to send over the border. (Many of the same people who were in power and did absolutely nothing to punish Iran for this - or even rewarded them for it - would later screech their heads off when Trump turned Soleimani into meaty gibs. Make of that what you will.) Now review the scorecard:
Korea: Now highly stable and... about as healthy a democracy as any SE Asian nation has managed (lol Japan) at the cost of
decades of permanent military presence to guard them, adding up to untold trillions of dollars over the years since the Armistice. Oh, and a nuclear entanglement potential, too.
Vietnam: War was actually won, and then the government we supported and defended collapsed... after Democrats gained control of Congress and promptly chopped the funding support, throwing away everything thousands of Americans died for. Is that better or worse than the funding being cut
because the war itself was a key contributor to the collapse of the state that started it? 
Iraq: Actually, unambiguously won. Twice, first against Iran, then against ISIS. We won the prize, though not many people think it was worth the cost, given how much military modernization is yet to be done and the ever-nearer conflict with China. On the silver-linings side, Trump was in just long enough to prevent the usual fuckheads from making Kurdistan a permanent vassal state with an equally permanent US military commitment; because apparently
one Korea isn't enough!
Now, look at all that, and tell me - what do you think Putin's chances in Ukraine are, with fuel, food, medical supplies and weapons pouring into Ukraine through Poland?
Y'see, the tragedy of Afghanistan is that it could have gone very differently. If you want to fight a forever war, you have to
fight it AS a forever war. You commit to a strategy that you can afford to maintain indefinitely. In Afghanistan's case, that means you set up shop in that one province the Taliban never did manage to subjugate, and let the Taliban "have" Afghanistan. And every now and then you send some high-speed-low-drag boys outside the wire in the dark of night and they come back with a few severed heads. If the Taliban want Afghanistan? Let them have it! Let
them run constant patrols. Let
them keep one eye on the sky, always wondering if there's a Reaper with a laser paint on their dome. That's a cheap way to fight. The Taliban were able to fight asymmetric war for two decades with RPGs and rifles, and if it had taken 40 years for more pressing spending priorities to crop up for the Americans, they could've done that, too. But have you seen asymmetric war with the toys
we have? With Switchblade drones and Javelin missiles and- oh. Well. I guess you have
now, haven't you?
You know who
else has all those toys? Yeah. You know the guy. You know who has all those toys but not nearly enough of them to go
balls deep into the ant nest for twenty fucking years like the Americans did? Yeah. Same guy. You do the math on how this ends.
