PERSIAN GULF

In Middle East, US wants to maintain access to oil and gas, and partners against terrorism and Iran.

WHAT US INVESTS

■ Pledge to defend the free flow of oil and gas (known as the Carter Doctrine) ■ Implicit promise to defend allies against Iran

WHAT IT GETS BACK

■ Counterterrorism, intelligence-sharing against Islamist terrorists and Iran ■ Access to 34% of the world’s oil exports, 16% of natural gas exports ■ Allies cover 60% of basing costs, which is $ 658 million annually ■ Bases near, and allies united against, Iran