Explainer: Why does the US pay so much for the defense of its allies?

When stronger countries provide security for weaker countries, they receive non-material benefits in return.

For example, the weaker country may sacrifice control over their foreign policy and give the major power access to territory or airspace it otherwise would not have. Deployments in Japan and Korea gave the U.S. influence in Southeast and East Asian regional matters during the Cold War.

Additionally, U.S. military personnel have served as the forefront of U.S. public diplomacy over the past 70 years through their routine jobs and day-to-day interactions with locals. The U.S. has been particularly effective at building “soft power,” meaning that people in other countries support the U.S. because of the affinity they feel toward Americans and American culture. Negotiations with South Korea previously occurred every four to five years. The Trump administration changed this last year to every year for South Korea. These negotiations are complicated and could make annual negotiations both time-consuming and turbulent. Second, reports suggest that Trump’s new demands are not based on any clear U.S. military need. This leads us to the question of how Trump arrived at the new sum being sought from South Korea.