National power includes the ability to influence events, although no state can control every other participant. On a shared river, prolonged customs checks offer one way to obstruct another country's trade. A state without river capability may have little practical response. With its own vessels, it can threaten comparable delays to its neighbours' traffic. In this example, the prospect of mutual inconvenience encourages negotiation.
Notable Point · 38:06-41:29
River flotillas as political leverage
Reciprocal customs delays illustrate how river patrol capability can give a smaller state leverage over shared trade routes.