Freedom of the seas is one of Wilson's Fourteen Points, according to which the open sea is free for all and no state can hold sovereignty on it. So in the high seas freedom of navigation applies, as well as free fishing, and the only state that can exercise control over a ship is the very state whose flag the ship is carrying.
This principle sought to avoid international conflicts by declaring ocean waters as international, therefore neutral and not belonging to any state, with which no state could attempt to conflict with another for issues related to the high seas, which at the time was the main transport channel for people and goods in the world.
The Mongols claimed the largest consolidated land empire in history. Seemingly the only way to keep them out was to put the Himalayas between you and them. And many historians believe their power stemmed from an incredibly simple technological innovation: the stirrup.
