I had a history teacher in middle school who would rub his thumb to his index finger and say it with an all-knowing grin on his face - "it's all about the money." He prided himself for being so enlightened despite being a history teacher - you know you can get bogged down in so many beside-the-point details when you teach history. You might get carried away talking about battles and castles and tents and rivalries and power and the eccentric traits of the leader and revenge and honour and pride and love. My history teacher had a thing for horses and Turks' horsemenship, for example. But he didn't let any of it blur his sight and blind his judgement. He knew that the reason for all wars was money.
That's nothing original. Why do the Westerners intervene in Iraq of all places? Are we supposed to believe they are so idealistic? It's the same story all over again - the elites mobilize the masses for purely economic reasons, personal ambitions and grudges. They use idealistic motives, heroic stories and well-substantiated fear to add some meaning to the story. Otherwise, how could young people be convinced to put their lives at stake?
As more people die, the fog of irrationality and myth thickens, it becomes all the more difficult to admit to mistakes. How can one explain - were all those lives lost and taken simply because of poor judgment, poor foresight? Was it just senseless war?
Then the variables shift, your foreign presence tips the balances and it is no longer reasonable to go out of a place you weren't supposed to go into in the first place. The stalemate becomes the new status quo. People who invested their lives in it cannot bring themselves to accept anything short of victory. You can't close down a factory that continues to run losses, because the sunk costs are already too large. The wrestler who loses always wants another round.
As time goes by, the war takes on a meaning of itself, one that is independent of the initial motives and goals. The lives and time lost give it a new meaning. That is when it becomes so difficult to give up and walk away.