Overseas trips by politicians and military leaders are all about sending messages. So what messages are being sent by US Defense Secretary Ash Carter's ongoing visit to the Philippines?

The clearest is the US military intends to strengthen its presence in the South China Sea, which poses more threats to regional peace and stability.

As part of its "pivot to Asia" strategy, the United States has been shifting its military back to the region. Carter's trip reveals the US has put that process back on a fast track, with the expectation it will establish more bases in the Philippines.