In addition, we devote Department of Energy funds to petroleum research. Hard to say. Even without the presence of oil, some troops might be stationed in oil-rich areas for other reasons. What is more, troops can be mobilized worldwide if necessary. Direct calculation of such a cost is virtually impossible.
Indirect calculation is, however, possible.
According to a former Assistant Secretary of Defense for Economic Security, we currently have about 17,000 troops in the Persian Gulf. Most researchers have estimated annual expenses toward the high end of this range. Naturally, none of these figures count the costs of pain and suffering to U.S. soldiers, nor costs to our adversaries. We don't fight such wars every year. One Defense Department official speculated that the Gulf War might keep things quiet for up to 10 years.