The question is, where is the line between policing and defense.
For example, is having a substantial military force in the Persian Gulf to act as a check on Iran and maintain the flow of oil to major trading partners policing, or defense? Is maintaining a substantial military force in the Western Pacific as a deterrent to China’s territorial claims policing or defense? Is maintaining a substantial military force in the Horn of Africa to protect the free flow of commerce from piracy policing or defense?
In a world where an enemy can get around the world in a matter of minutes, a nation is not defended if they’re confined to their own borders.