What Goes Around Comes Around

The original "Thucydides trap" was Sparta (a land power) fearing the rising (sea) power of Athens. Sparta's King Archidamus urged restraint rather than war. He was cited in Britain's House of Commons on 18 March 2003 by an MP who opposed the invasion of Iraq. But in the 5th century BC Athens' democratic leader Pericles argued that concessions would be interpreted as weakness. Athens lost the war.
The early years of the 20th century were an example of Thucydides' (an Athenian general) theory. Germany (a land power) was rising. Britain (a sea power) was afraid.
Today the rising power, China, is building airfields on islets in the South China Sea and claiming the Sea as its own.
Only the existing power (the US) can stop them.
Both Athens and Sparta had allies. So did Britain and Germany 100 years ago.
Weaker countries bordering the South China Sea look to the US to help them....
Thucydides believed that war in one place caused a movement of people and so another war....