The Western Hemisphere is to be protected from imperial aims from nations, specifically European nations, outside the Western Hemisphere. This policy was first formulated by James Monroe and John Quincy Adams. Dubbed the Monroe Doctrine, it has informed and influenced U.S. foreign policy within the region ever since.

At the time, Monroe was concerned about protecting and promoting U.S. regional influence over and against the European powers. This foreign policy effectively told the Europeans that the Western Hemisphere was our sandbox and warned them to stay out and play in their own sandbox. The goal was to protect the interests of the U.S. by limiting European nations’ influence in the region.

Early on, it had a spirit of isolationism. The world was big enough for Europe to stay in its own sandbox and leave the U.S. alone.

However, as technological developments shrank the world and the demand for goods and trade increased, isolationism became practically impossible. Under Teddy Roosevelt, the Monroe Doctrine expanded with the addition of the Roosevelt Corollary, which established the policy of the U.S. using its military to enforce its regional influence over and against other powers.

Fast-forward to today, and Donald Trump is once again unashamedly engaging the Monroe Doctrine in an effort to counter China’s expanding influence operation in the Western Hemisphere.

At issue is the Panama Canal. Trump has repeatedly noted that it was a mistake for Jimmy Carter to give it up, and he says he intends to take it back. Of course, Panama has no interest in giving back the canal zone. But it clearly got the message.

In roughly 24 hours, Secretary of State Marco Rubio met with Panama President José Raúl Mulino and negotiated a deal that thwarts China’s influence campaign. Calling it an era of new cooperation, Rubio stated, “I think this visit opens the door to build new relations … and try to increase as much as possible U.S. investments in Panama.”

Panama has agreed to end its cooperation with Beijing with its Belt and Road Initiative. This is significant since Panama was the first Latin American country to join China’s BRI. This could result in a domino effect in the region; with a bit of U.S. pressure, more Latin American countries could dump the BRI.

Furthermore, Panama has agreed to take measures to prevent South American migrants from passing through the isthmus.

Like Greenland, the Panama Canal is a strategic region that the U.S. cannot let fall under China’s control. Roughly 72% of the ships that pass through the canal are headed to or from American ports. The canal’s impact on U.S. national security and our economy would be difficult to overestimate.

This Panama deal has been yet another big success for Trump’s foreign policy efforts. He knows he’s got a big stick — the power of the world’s number one economy — and he’s not afraid to swing it.