For the past year or so, senior U.S. government officials have been accusing China of engaging in so-called “debtbook diplomacy,” a tactic that Washington contends intentionally burdens developing countries with billions of dollars of loans. When these countries, many of them some of the poorest in the world, invariably can’t pay back the loans, Beijing extracts concessions that further China’s geopolitical interests, according to the theory that is now widely held among U.S. politicians, academics, and strategists.