Jeffrey Sachs goes back to 1943.
"At the Cairo Conference... it said that those territories that had been seized by Japanese imperialism... would be returned to China. This was absolutely clear, and Taiwan was on that list."
The Cairo Declaration, signed by Roosevelt, Churchill and Chiang Kai-shek, names it : Formosa and the Pescadores "shall be restored" to China.
Potsdam 1945 repeated it. UN Resolution 2758 in 1971 settled who holds China's seat.
Even after the civil war, Sachs says, the fight was over whose China it was. Never whether Taiwan was part of it.
So how did it become a "geopolitical issue" ?
"Because the United States unfortunately is making provocations."
His advice to Washington, in one line :
"Don't make trouble where you shouldn't make trouble."
History wrote it down 80 years ago. The arms dealers just never read it.