why? Do we need troops all over the world?

Of course the opposite of troops all over the world is "isolationism", to withdraw to within our borders and be self sufficient in all areas. This presence all over the world stems from the old rich man theory. That is that rich people(or nations) have an obligation to help their fellow man. It does follow that "but for the grace of God, there go I" and rich people or rich nations should recognize a kind of duty to help others. Now until lately, America has been a rich nation and our presence around world is driven in part by "duty" to help others. But certainly it is also driven by corporate greed and war.

It does appear to me that our worldly presence has been greatly driven by corporations seeking profit and in particular, OIL. And, by the way, I believe it is historically true that being occupied or controlled by foreigners creates hatred(due to territorial instinct)and has resulted in terrorism. Terrorism is defined as the use of force or threats to demoralize, intimidate, and subjugate, esp. such use as a political weapon or policy against rich,more powerful nations or entities.

So out of this discussion is there an answer to the question, why do we need troops all over the world? Very simply put the answer is the need for oil and to combat terrorism. A solution, return to Isolationism.