2,500 hundred years ago, one of the greatest military strategists ever - Sun Tzu - said:
- "What is essential in war is victory, not prolonged operations."
- "No nation has ever benefited from a prolonged war."
- "Now, when an army of one hundred thousand is raised and dispatched on a distant campaign, the expenses borne by the people together with disbursements of the treasury will amount to a thousand pieces of gold daily. In addition, there will be continuous commotion both at home and abroad, people will be exhausted by the corvee of transport, and the farm work of seven hundred thousand households will be disrupted."
"A thousand pieces of gold" is a metaphorical, not set, amount. The costs of today's wars are actually much higher than a ton of gold per day.
Despite the talk of withdrawal, America is engaged in perpetual war in the Middle East (and see this, this, this, this, this and this).
America's political leaders haven't learned a 2,500-year-old lesson.
And see this.