History demonstrates incontrovertibly that nations do what they do because they can. It is one of the more flippant reasons Dick Cheney is reported to have given in answer to the question why the U. S. invaded Iraq.
When Britain ruled the waves, no foreign ship nor citizens nor indeed nations were safe. Remember the War of 1812? The British burned Washington DC all because the U. S. objected to the seizure of American ships (sailing perhaps to trade with and/or aid the French) and the impressment of Americans into the British navy. Things could have gotten uglier but for the realization on the part of the Brits that they had a great deal more to lose in Canada. (That they lost it in the end didn't happen until over a hundred years later, so it doesn't matter.) The Brits found easier naval operations to execute, including two Opium Wars visited upon China in the name of free trade.
On its part, America took to heart Alfred Mahan's dictum to ensure its own "possession of that overbearing power on the sea which drives the enemy's flag from it, or allows it to appear only as a fugitive; and which, by controlling the great common, closes the highways by which commerce moves to and from the enemy's shores." Certainly it reinforced the Monroe Doctrine, though it is not clear what the Latin Americans thought then. (What they think now is clear.)
The surprise and indignation displayed over China's actions and intentions in the South Sea has a self-serving ring. The above map showing the People's Republic now infamous "9 dotted line" is by U.S. Central Intelligence Agency - Asia Maps — Perry-Castañeda Map Collection: South China Sea (Islands) 1988. Licensed under Public Domain via Wikimedia Commons. What China really intends to achieve remains a mystery. Is it the possibility of energy reserves to be gained? Or is it simply to demonstrate that it now can do this?
The Ninja and the Diplomat, now available although technical issues remain, explores this tangentially. Spymaster Wang and an assistant finance minister discuss this, touching on directional drilling and binding arbitration among other subjects, and concluding with the following excerpt:
“Thank you for this lesson. I do not know what a national security expert or a finance minister should do in a dispute involving military and foreign policy interests. But I was concerned from a national security point of view.”
“And I am concerned from an economic financial point of view,” interrupted Zhang. “It really bothers me that those who are ready to go to the brink of war have not counted the cost of their preference or weighed it against the cost of the alternatives.”
“You were right, Comrade Zhang,” agreed Wang. “Your views are not only unconventional, they are heretical. If we believed in wizards and witches, you would be dealt with accordingly.”
The assistant minister laughed, but insisted, “The water is far and the fire is near. Why are we so stupid?”